How to use Cell in a sentence
The cell reproduced and the organism grew.
In every cell of your body except your red blood cells exists a copy of your DNA.
In 1902, an American named Walter Sutton noticed that chromosomes duplicated themselves before cells divided so that each new cell had a full copy of the chromosomes.
We were startled by the ring of my cell phone.
I tried to call you on your cell phone, but I didn't get an answer.Advertisement
My cell phone alerted me to a message.
Each cell measures 35 cub.
Rhyn made a racket in his cell.
He took her to the holding cell.
He retreated to his cell and sat against the wall again, troubled by a familiar feeling of helplessness.Advertisement
She.d last seen him in Hell, where they shared a cell together.
He slunk down to the holding cell to face the music.
Gabriel's furious curse made Toby jump. Toby looked his direction the best he could through the bars of his cell and saw the walls around the dark cell shake.
Usually the cytoplasm shows a marked affinity for the acid stains, but the different bodies found in the cell may show great variation in their staining reactions.
Cell in a state of degeneration and chromatolysis; the large rounded body in the cell is a cancer parasite.Advertisement
Then we have the property of adaptation, in which the negative reaction may be changed into a positive; a given toxin may at first repel the cell, but by a gradual process the cell becomes accustomed to such a toxin and will move towards it.
Where the material is too large to be taken up by an individual cell, the dissolution is brought about by the cells surrounding the material, to which they closely apply themselves, and by the secreting of the ferment, a gradual process of erosion is brought about with ultimate absorption.
Midnight was long past when Savonarola was led back to his cell.
The animal cell can absorb its carbohydrate and proteid food only in the form of carbohydrate and proteid; it is dependent, in fact, on the pre-existence of these organic substances, themselves the products of living matter, and in this respect the animal is essentially a parasite on existing animal and plant life.
The sounds of Rhyn slamming his body into his cell and snarling awoke her sometime later.Advertisement
She eyed the door at the end of the hall, then her cell, and turned 360.
She'd lived through too much the past few days to be eaten by some boogeyman in a dark cell!
She dressed quickly to avoid comments on either her collar or her scars and flung herself into her bunk, reminded of her cell with Lankha.
She didn.t remember him being so tall in Hell, but she.d been afraid to look too hard at him when she passed his cell.
I think sometimes I should.ve moved into the cell beside yours in Hell.Advertisement
When Ne'Rin signaled all was ready, he strode from the deck into the corridor and straight to her cell.
The cell where she sat measured six by six with a grey bench.
The 'holding cell' was a lavishly appointed 700 square foot room.
The human had spent most of the evening pacing around the cell, trying to make some sense of everything, stopping only briefly to eat, in an effort to soak up all the alcohol.
Connor's description of being in the holding cell 'losing his mind and living a nightmare' accurately described his feelings.
Elisabeth stared straight ahead, then picked up her cell phone and walked out of the kitchen.
They walked in silence to the holding cell.
Okay, let me give you my cell number.
The three sat in the kitchenette of the holding cell since Sarah refused to leave Connor, even for a minute.
He found Sarah and Connor on the sofa in the holding cell.
Maybe you could just give me her cell number.
Toby huddled against the black stone wall of his cell in Hell.
Ully called from the cell across the narrow hallway.
Toby looked up as the familiar demon named Jared passed his cell, trailed by two demons carrying a body with another familiar face.
His long time friend, the assassin, was bloodied and unconscious. The demons tossed Gabriel's body into a dark cell two down from Ully's before they left.
I have more freedom than you when I'm not in this cell.
Do you have your cell phone?
Keep your cell phone handy.
The somatic cells represent communities or republics, as it were, which we name organs and tissues, but each cell possesses a certain autonomy and independence of action, and exhibits phenomena which are indicative of vitality.
Still, it must be borne in mind that this alleged autonomy of action is said to be founded upon an erroneous supposition, on the supposition that each cell is structurally, and it may be said functionally, separated from those in its neighbourhood.
It is well known that in the vegetable kingdom the protoplasm of one cell frequently overflows into that of cells adjacent - that there is, as it were, a continuous network of protoplasm (idioplasm of Nageli) prevailing throughout vegetable tissues, rather than an aggregation of isolated units.
Until, however, further evidence is forthcoming in support of this syncytial theory of structure, it would be unwise to regard it as established sufficiently to constitute a serviceable working hypothesis; hence, for the time being, we must accept the assertion that the cell represents the ultimate tissue-unit.
Our present day definition of a cell is a minute portion of living organized substance or protoplasm.
The cell body, or cytoplasm, is apparently composed of a fine reticulum or network, containing within the meshes a soft viscid, transparent substance, the cell-sap, or hyaloplasm, which is probably a nutrient material to the living cell.
Pigmented cell with resting nucleus.
We have already compared the body to a social community, each constituent element of which - the cell - lives its own life but subordinates its individuality to the good of the whole organism.
The epithelial cells are then able to pass from their normal position, in consequence of which they proliferate and at the same time revert to a more primitive type of cell.
Hansemann's "anaplasia " hypothesis seeks to find an explanation of the formation of new growths in the absence of the histological differentiation of the cell associated with a corresponding increase in its proliferative power and a suspension, or loss, of its functional activity.
Some workers regard certain appearances in dividing cells found in cancer as evidence of a reversion of the somatic cell to the germcell type (heterotypical), otherwise found only in the process which results in the formation of an embryo.
Oertel finds an explanation of this want of complete celldifferentiation, loss of function, and acquired vegetative activity in the non-homogeneous character of the nuclear chromatin elements of the cell, and maintains that the different properties of the cell are carried and handed down by the different orders of chromatin loops.
We have analogies to this in the two nuclei of some of the protozoa, the one being solely for the purpose of propagation, the other being associated with the functional activities of the cell.
If, from whatever cause, any of the chromatin loops belonging to the functional order be lost the descendants of such a cell, being unable to restore these loops, will be minus the functional attributes associated with the lost elements.
The foregoing hypotheses have all sought the origin of new growths in some intrinsic cause which has altered the characters of the cell or cells which gave rise to them, but none of them explain the direct exciting cause.
Autolysis is a disintegration of dead tissues brought about by the action of their own ferments, while degeneration takes place in the still living cell.
There it is acted on by ferments (lipases) and converted into neutral fat, which may remain in the cell as such.
By the reverse action on the part of the same ferments in the cell, these neutral fats may be redissolved and pass into the.lacteals.
As fat is a food element essential to the carrying out of the vital energies of the cell, a certain amount of fatty matter must be present, in a form, however, unrecognizable by our present microchemical and staining methods.
This splitting up of the fats previously combined with albumin in the cell by the action of natural ferments - lipases - and the setting free of the fats under the influence of toxins represent the normal and the pathological process in the production of so-called fatty degeneration.
It can be formed independently of cell activity, nor does it require oxygen.
The liver cells are seen to contain a large globule of fat which pushes the cell nucleus to one side - giving the signet-ring appearance.
Hyaline degeneration is found in certain acute infective conditions; the toxins specially act on these connective-tissue cell elements.
The ovary bears a sessile stigma and is more or less completely two-celled, with two erect ovules in each cell.
A cell when filled with fresh slices becomes the head of the battery, and where skilled scientific control can be relied upon to regulate the process, the best and most economical way of heating the slices, previous to admitting the hot liquor from the next cell, is by direct steam; but as the slightest inattention or carelessness in the admission of direct steam might have the effect of inverting sugar and thereby causing the loss of some portion of saccharine in the slices, water heaters are generally used, through which water is passed and heated up previous to admission to the freshly-filled cell.
When once a cell is filled up and the slices are warmed through, the liquor from the adjoining cell, which hitherto has been running out of it to the saturators, is turned into the new cell, and beginning to displace the juice from the fresh slices, runs thence to the saturators.
When the new cell comes into operation and becomes the head of the battery, the first or tail cell is thrown out, and number two becomes the tail cell, and so the rounds are repeated; one cell is always being emptied and one filled or charged with slices and heated up, the latter becoming the head of the battery as soon as it is ready.
Each cell is of suitable dimensions to turn out a slab of sugar about 14 in.
The ovum first divides into (a) a granular cell, and (b) a cell full of refringent spherules.
Assassins were sent to kill him in his cell; but awed, it is said, by Savonarola's words and demeanour they fled dismayed from his presence.
Mounting his own pulpit in St Mark's he quietly related the events of the day to the faithful assembled in the church, and then withdrew to his cell, while the mob on the square outside was clamouring for his blood.
The prisoners were conveyed to the Palazzo Vecchio, and Savonarola was lodged in the tower cell which had once harboured Cosimo de' Medici.
The vaults are gracefully painted with floreated bands along the ribs and central patterns in each "cell," in rich soft colours on a white plastered ground.
When an alkaline chloride, say sodium chloride, is electrolysed with one electrode immersed in a porous cell, while caustic soda is formed at the cathode, chlorine is deposited at the anode.
Hypochlorites were made, at ordinary temperatures, and chlorates at higher temperatures, in a cell without a partition in which the cathode was placed horizontally immediately above the anode, to favour the mixing of the ascending chlorine with the descending caustic solution.
Similarly, the formation of organic halogen products may be effected by electrolytic chlorine, as, for example, in the production of chloral by the gradual introduction of alcohol into an anode cell in which the electrolyte is a strong solution of potassium chloride.
Accordingly the number of electric cells into which the space round is cut up is equal to twice the energy stored up, or each cell contains half a unit of energy.
The cuticle is secreted by an epidermis in which no cell boundaries are to be seen; it sends out processes into the bristles.
Great numbers of monks, each in solitary cell, spent lonely lives, scorched by the sun, ill-clad and scantily fed, pondering on portions of Scripture or copying MSS.
This monastery was restored in the reign of Robert Bruce, and became a cell of the abbey of canons regular at Inchaffray.
Such, for instance, were those of Spindler and Wrangell in the Black Sea by sinking an electric lamp, those of Paul Regnard by measuring the change of electric resistance in a selenium cell or the chemical action of the light on a mixture of chlorine and hydrogen, by which he found a very rapid diminution in the intensity of light even in the surface layers of water.
A small brook named Barri runs here into the sea, whence the place was formerly known in Welsh as Aber-Barri, but the name of both the river and the island is supposed to be derived from Baruch, a Welsh saint of the 7th century, who had a cell on the island.
The central authorities, which as early as the 18th century worked together in a common mother cell of the State chancery, became differentiated so soon as the growing tasks of administration called for specialization; in 1869 there were seven departments, and in the concluding decade of the Austrian Empire there were set up Ministries of Labour, Food, Public Health and Social Care.
Returning to his cell he continued a labour in which he had been engaged, the transcription of the Psalter.
It consisted of a glass vessel, containing a solution of sulphate of zinc, in which were placed two plates of pure amalgamated zinc. These plates were connected by means of a german-silver shunt, their size and the distance between them being so adjusted that about ii 0 - 0 - part of the current passing through the meter travelled through the electrolytic cell and -j o i j of the current passed through the shunt.
The shunted voltameter was then inserted in series with the electric supply mains leading to the house or building taking electric energy, and the current which passed dissolved the zinc from one plate and deposited it upon the other, so that after a certain interval of time had elapsed the altered weight of the plates enabled the quantity of electricity to be determined from the known fact that an electric current of one ampere, flowing for one hour, removes 1.2533 grammes of zinc from a solution of sulphate of zinc. Hence the quantity in amperehours passing through the electrolytic cell being known and the fraction of the whole quantity taken by the cell being known, the quantity supplied to the house was determined.
To prevent temperature from affecting the shunt ratio, Edison joined in series with the electrolytic cell a copper coil the resistance of which increased with a rise of temperature by the same amount that the electrolyte decreased.
Only the two gran it will take to put the lines down this way, and cell phone reception is unreliable.
Toby asked, pressing his face against the cell door.
Rhyn left the cell block to Toby's protests and walked with Gabe through the antechamber and into the hallway on the other side. Gabe's gaze was dark, his air brooding. Rhyn opened a portal, and they crossed through to Gabe's cabin in the underworld.
Toby felt almost as distraught at having to stay in the cell while his human was lost in the underworld. Not that he didn't trust Rhyn or Gabe, just that, he might be able to find her first.
As Toby watched, Ully stuck his hand out of the cell and placed it on the wall.
His cell door clicked open. Toby bounced to his feet.
Ully returned a couple of minutes later. He strode to Toby's cell and dangled the talisman before it. Toby's door opened.
Toby stepped out of the cell and closed it.
He heard Hannah crying and smelled the unmistakable scent of human blood before he took a step onto the block. He strode down the block and paused in front of Hannah's cell. She was curled up on the bed, sobbing. When he looked at the cell across from her, he saw why. Jared stood in the cell, covered in blood. The cell looked as if a human had exploded, and Rhyn saw a pile of bones Jared had gnawed clean then stacked neatly.
He placed the talisman on the door frame of Hannah's cell. The door opened.
Rhyn ignored the demon and left the cell block, returning to the hallway before opening a portal. He crossed through the shadow world to the beach of the Caribbean Sanctuary. Toby was dragging Kiki up the beach by one leg.
I'm not used to having a phone in the house, much less carrying a cell phone.
Her cell phone was in her pocket, but Alex probably figured she didn't have it with her.
Do you have your cell phone with you?
She took her time getting home, ignoring her cell phone when it rang.
He was probably upset that she didn't answer her cell phone, but he had given her strict orders not to use it when she was driving.
She had forgotten her cell phone on the dresser again.
Ten O'clock found her hanging over the telephone, her cell phone on her hip.
She threw her cell phone on the bed.
If she hadn't thrown her cell phone on the bed, she could have called him.
Can I borrow your cell? she asked.
Sofi had taught him to use his cell phone and Dusty had taught him the computer.
She pocketed the cell, grateful for his consideration.
Jenn scoured their cell.
There were no weaknesses to the cell.
Sofi appeared relaxed in the cell, her head resting against the wall and her brilliant eyes focused on Jenn.
In order to find her, the first guardsmen would have to enter the cell.
Another fell, and the third shoved her into the cell.
She strained to keep her hold on the guardsman, even as the other one left the cell and snatched a sword to finish her off.
Returning to the cell, she used the long-sleeved shirt to wipe the blood off her body quickly and then to clean the blades of the weapons she snatched off the ground.
The heavy, musty scent of earth was contained within a four-by-four-foot cell, not even large enough for him to lie down.
Before she fell again for Sirian's lies, she pushed the lever to seal his cell and walked away, rage and confusion making her head spin.
The iron wall was open in front of Sirian's cell.
The cell holding Sirian was closed.
Hilden caught up to them as they reached the dungeon, where Vara was opening the iron door to the cell containing Sirian.
Memon ignored him, darting into the cell where the unconscious Rissa lay.
Vara hurried to close the iron door while Hilden rushed to the cell holding Memon.
Vara pulled her body towards him until she cleared the cell then lifted her.
Both cell doors had exploded off the cells and lay crumpled across the room.
Memon's lifeless body was wedged between the bars of one cell.
I gave him your cell phone number.
Their lovemaking lasted only a few minutes before his cell phone rang.
Did you know Jonathan told our twins that Alex wants to get him a cell phone but you're being a … unreasonable about it?
Jonathan had reached puberty in full rebellion, which was one of the reasons she didn't think he should have a cell phone.
Fortunately Morino saw the ad for Apple Hors Devours in the local paper and recognized Alfonso's cell phone number before they made their first sale.
Alfonso lost the use of his cell phone for a month and Alex grounded Jonathan for the same amount of time.
That evening at home they were eating supper when Jonathan again asked Alex if he could get a cell phone.
They had badgered the parents of their thirteen year old member into getting him a cell phone and then had started on Carmen.
Later Carmen and Alex had explained to Jonathan that he was too young for the responsibility of a cell phone.
Pulling the cell phone from the holster on her side, she called Felipa.
Alex would be upset, but even worse; it would give Jonathan ammunition in his battle for a cell phone.
Remembering her cell phone, she reached for it.
She might as well figure on getting that cell phone for Jonathan.
Monday morning while Felipa took the men riding and the children were coloring, Carmen used her new cell phone to call the employment office.
If I had a cell phone, I could call you when I was ready.
Her cell phone rang at the exact time she was certain that her head would burst.
Pulling the cell phone from her purse, she tried calling Mr. O'Hara.
Apparently the area where the cabin sat was a dead spot for cell phones.
Another cell could develop at any time and this could start again all over.
This time her cell phone worked and a deep voice answered.
Once again she tried the cell phone, with the same results.
Brandon shoved a hand between the cushions and fished out the cell.
Brandon peppered her with questions, until she finally gave him her cell and let him listen to the messages.
She held up her cell.
An iPad in a bright green case and a cell phone labeled work phone!!!!! was sitting on the table in the informal dining area, a sticky note on it.
Rule five, keep your cell on.
The work cell rang, and she picked it up, answering instinctively.
I'll give you my cell number.
When you feel like venting, call, Gerry said and picked up her cell.
She fished the cell out of her purse and frowned.
Suddenly, she smiled and grabbed her cell phone.
I GPS tagged my cousins' cell phones and wallets.
Yeah. Only it wasn't just your cell and wallet.
A text drew her attention to the cell phone.
Xander tossed him the cell, and Darian strode out of the barn.
Making sure she's not sneaking up behind me to kill me, Xander said and removed his cell from his jeans.
Several were in Southern California while two blue dots – the one in her cell phone and the other in a shoe – appeared on the map in Texas.
Heart pounding hard, she sat on the bed and pulled out her cell phone.
He took Jessi's arm then whipped out his cell with his free hand.
Traube (1858), the active cause of fermentation is due to the action of different enzymes contained in yeast and not to the yeast cell itself.
He agreed with Pasteur that the presence of living cells is essential to the transformation of sugar into alcohol, but dissented from the view that the process occurs within the cell.
This investigator held that the decomposition of the sugar molecules takes place outside the cell wall.
This body is being continually formed in the yeast cell, and decomposes the sugar which has diffused into the cell.
In this respect the plasma behaves in a similar manner towards the sugars as does the living yeast cell.
He emphasized the opinion that yeast derived from one cell was of no good for top fermentation, and advocated Pasteur's method of purification.
In the United Kingdom the employment of brewery yeasts selected from a single cell has not come into general use; it may probably be accounted for in a great measure by conservatism and the wrong application of Hansen's theories.
The flasks were then well shaken, and the yeast cell or cells settled to the bottom, and gave rise to a separate yeast speck.
To obtain an absolutely pure culture with certainty it is necessary, even when the gelatin method is employed, to start from a single cell.
Fermentation now includes all changes in organic compounds brought about by ferments elaborated in the living animal or vegetable cell.
In most cases four spores are formed within the cell by free formation.
In a monastery at Naples, near the cathedral of St Januarius, is still shown a cell in which he is said to have lived.
In some species (Ascaris decipiens) the giant cell is replaced by an irregular mass of protoplasm containing a number of small nuclei.
Each cell contains a zinc plate, immersed in a solution of zinc sulphate, and also a porous chamber containing crystals of copper sulphate and a copper plate.
The electromotive force of each cell is i 07 volts and the resistance 3 ohms. The Fuller bichromate battery consists of an outer jar containing a solution of bichromate of potash and sulphuric acid, in which a plate of hard carbon is immersed; in the jar there is also a porous pot containing dilute sulphuric acid and a small quantity (2 oz.) of mercury, in which stands a stout zinc rod.
The electromotive force of each cell is 2.14 volts, and the resistance 4.
The size of the accumulators employed varies from a cell capable of an output of 8 ampere-hours, to a size giving 750 ampere-hours.
A totally reflecting prism placed inside the glass cylinder projects the light which penetrates the film upon a selenium cell situated at the end of the cylinder.
To eliminate the sluggish action of the selenium transmitter a selenium cell similar to that at the transmitting station is arranged at the receiving apparatus, and exposed to precisely similar variations of light, the arrangement being such that the lag of this cell counteracts the lag of the transmitting cell.
When such a tube is inserted in series with a single voltaic cell and galvanometer it is found that the resistance of the tube is nearly infinite, provided the filings are not too tightly squeezed.
On creating an electric spark or wave in the neighbourhood of the tube the resistance suddenly falls to a few ohms and the cell sends a current through it.
At the receiving station Marconi connected a single voltaic cell B 1 and a sensitive telegraphic relay R in series with his tube of metallic filings C, and interposed certain little coils called choking coils.
In series with the tube is placed a single voltaic cell and a telegraphic relay, and Marconi added certain coils placed across the spark contacts of the relay to prevent the local sparks affecting the coherer.
In later improvements the secondary circuit of this jigger was interrupted by a small condenser, and the terminals of the relay and local cell were connected to the plates of this condenser, whilst the sensitive tube was attached to the outer ends of the secondary circuit.
This increases the resistance of the electrolytic cell.
If, however, one electrode of this cell is connected to the earth and the other to a receiving antenna and electric waves allowed to fall on the antenna, the oscillations passing through the electrolytic cell will remove the polarization and L temporarily decrease the resistance of the cell.
The receiving arrangements comprised also an open or antenna circuit connected directly with a closed condenser-inductance circuit, but in place of the spark gap in the transmitter an electrolytic receiver was inserted, having in connexion with it as indicator a voltaic cell and telephone.
It is largely used for the purpose of making standard electric cells, such for example as the Weston cell.
He sometimes held the carbon powder against the diaphragm in a small tr ans' shallow cell (from a quarter to half an inch in diameter and about an eighth of an inch deep), and sometimes he used what he describes as a fluff, that is, a little brush of silk fibre with plumbago rubbed into it.
A large nematocyst, with everted thread, is seen in the right-hand ectodermal cell.
The cnidoblasts are the mother-cells of the nematocysts, each cell producing one nematocyst in its interior.
A further stage in evolution is that the muscle-cells lose their connexion with the epithelium and come to lie entirely beneath it, forming a sub-epithelial contractile layer, developed chiefly in the tentacles of the polyp. The of the evolution of the ganglioncells is probably similar; an epithelial cell develops processes of nervous nature from the base, which come into connexion with the bases of the sensory cells, with the muscular cells, and with the similar processes of other nerve-cells; next the nerve-cell loses its connexion with the outer epithelium and becomes a sub-epithelial ganglion-cell which is closely connected with the muscular layer, conveying stimuli from the sensory cells to the contractile elements.
The uppermost is a purely muscular cell from the sub-umbrella; the two lower are epidermo-muscular cells from the base of a tentacle; the upstanding nucleated portion forms part of the epidermal mosaic on the free surface of the body.
If the germ-cells are undifferentiated, the offspring may arise from many cells or from a single cell; the first type is (4) germinal budding, the second is (5) sporogony.
The spore-cell multiplies by division, while the enveloping cell is nutrient and protective.
The spore cell gives rise to a " sporelarva," which is set free in the coelenteron and grows into a medusa.
In Hydra the odcyte is a large amoeboid cell, which sends out pseudopodia amongst the odgonia and absorbs nutriment from them.
The result of cleavage in all cases is a typical blastula, which when set free becomes oval and develops a flagellum to each cell, but when not set free, it remains spherical in form and has no flagella.
Thallophyta are the most lowly organized plants and include a great variety of forms, the vegetative portion of which consists of a single cell or a number of cells forming a more or less branched thallus.
The male gametophyte is represented by one or few cells and, except in a few primitive forms where the male cell still retains the motile character as in the Pteridophyta, is carried passively to the macrospore in a development of the pollen grain, the pollen tube.
The male gametophyte is sometimes represented by a transitory prothallial cell;, the two male cells are carried passively down into the ovary and into the mouth of the ovule by means of the pollen-tube.
The female gametophyte is extremely reduced; there is a sexual apparatus of naked cells, one of which is the egg-cell which, after fusion with a male cell, divides to form a large siispensorial cell and a terminal embryo.
The term Anatomy, originally employed in biological science to denote a description of the facts of structure revealed on cutting up an organism, whether with or without the aid of lenses for the purposes of magnification, is restricted in the present article, in accordance with a common modern use, to those facts of internal structure not concerned with the constitution of the individual cell, the structural unit of which the plant is composed.
An account of the structure of plants naturally begins with the cell which is the proximate unit of organic structure.
The cell is essentially an individualized mass of protoplasm containing a differentiated protoplasmic body, called a nucleus.
A, Cell (individual) of the unicellular Green Alga Pleurococcus, as an example of an undifferentiated autonomous assimilating cell.
The primitive cell sends colorless tubelets (rhizoids, rh.) into the mud on which it grows.
The basal cell has less chlorophyll than the others, and is expanded and fixed firmly to the rock on which the plant grows by the basal surface, rh, thus forming a rudimentary rhizoid.
In such cases the characters of the adult tissue clearly depend solely upon the characters of the cell-walls, and it is usual in plant-anatomy to speak of the wall with its enclosed cavity as the cell, and the contained protoplasm or other substances, if present, as cell-contents.
Note thick walls and oblique slit-like pits with opposite inclination on the two sides of the cell seen in surface view.
It is from such a living and assimilating cell, performing as it does all the vital functions of a green plant, that, according to current theory, all the different cell-forms of a higher plant have been differentiated in the course of descent.
The cells Cell and are commonly joined end to end in simple or branched Tissue filaments.
In the group of the Siphoneae both these types of differentiation may exist in the single, long, branched, tube-like and multinucleate cell (coenocyte) which here forms the plant-body.
In Caulerpa the imitation of a higher plant by the differentiation of fixing, supporting and assimilating organs (root, stem and leaf) from different branches of the single cell is strikingly complete.
Each branch grows simply by the transverse division of its apical cell.
The cells belonging to any given thread may be recognized at an early stage of growth, because each cell is connected with its neighbors belonging to the same thread by two depressions or pits, one at each end.
Many of the lower forms of Brown Seaweeds (Phoeophyceae) have a thallus consisting of simple or branched cell threads, as in the green and red forms. The lateral union of the branches to form a solid thallus is not, however, so common, nor is it carried to so high a pitch of elaboration as in the Rhodophyceae.
In the Fucaceae, on the other hand, there is a single prismatic apical cell situated at the bottom of a groove at the growing apex of the thallus, which cuts off cells from its sides to add to the peripheral, and from its base to add to the central permanent cells.
The whole of the tissue of the plant is formed by the division of this apical cell.
In addition to the cell types described, it is a very common occurrence in these bulky forms for rhizoid-like branches of the cells to grow out, mostly from the cells at the periphery of the medulla, and grow down between the cells, strengthening the whole tissue, as in the Rhodophyceae.
It always consists of true parenchyma, and is entirely formed by the cutting off of segments from an apical cell.
The latter are plates of green tissue one cell thick, while the stem consists of uniform more or less elongated cylindrical cells.
The whole cavity of the cell is sometimes stuffed with proteid contents.
The end of the cell is slightly swollen, fitting on to the similar swollen end of the next leptoid of the row exactly after the fashion of a trumpet-hypha.
The leaf consists of a central midrib, several cells thick, and two wings, one cell thick.
The simplest type consists simply of a single elongated cell projecting above the general level of the lairs, epidermis.
The whole of the middle lamella or originally formed cell-wall separating one from another disappears before the adult state is reached, so that the walls of the hydroids consist of a framework of lignified bars, with open communication between the cell cavities.
On germination of the seed the radicle first grows out, increasing in size as a whole, and soon adding to its tissues by cell division at its apical growing-point.
In most Pteridophytes there is a single large apical cell at the end of each stem and root axis.
In other cases, again, a group of two or four prismatIl cells takes the place of the apical cell.
Apical cell, p. Wall marking limit between the plerome k, initial segment of root-cap. P and the pleriblem Pb.
The periblem, one cell thick at the apex, produces the cortex, to which the piliferous layer belongs in Monocotyledons; and the plerome, which is nearly always sharply separated from the periblem, gives rise to the vascular cylinder.
When a given initial cell of the cambium has once begun to produce cells of this sort it continues the process, so that a radial plate of parenchyma cells is formed stretching in one plane through the xylem and phloem.
Very soon the single cell gives rise to a chain of cells, and this in.
This is a primal necessity of the protoplast,and every cell gives evidence of its need by adopting one of the various ways in which such need is supplied.
The apparently structureless substance is saturated with it; and if once a cell is completely dried, even at a low temperature, in the enormous majority of cases its life iS gone and the restoration of water fails to enable it to recover.
The process involves the iqter-action of water also, and this, as we have seen, is always present in the cell.
But it is certain that it can only be present in a cell in very small amount at any moment, for an extremely dilute solution acts as a poison to protoplasm.
The formaldehyde at once undergoes a process of condensation oi- polymerization by the protoplasm of the plastid, while the hydrogen peroxide is said to be decomposed into water and free oxygen by another agency in the cell, of the nature of one of the enzymes of which we shall speak later.
As much sugar as is produced in excess of the immediate requirements of the cell is converted into the insoluble form of starch by the plastidsof the chlorophyll apparatus, and is so withdrawn from the sphere of action, thereby enabling the construction of further quantities of sugar to take place.
The presence of too much sugar in solution in the sap of the cell inhibits the activity of the chloroplasts; hence the necessity for its removal.
The idea of an identity of protoplasm does not involve a denial of special powers developed in it in different situations, and the possession of such a power by the vegetable cell is not more striking than the location of the powers of co-ordination and thought in the protoplasm of cells of the human brain.
The material and the energy go together, the decomposition of the one in the cell setting free the other, which is used at once in the vital processes of the cell, being in fact largely employed in constructing protoplasm or storing various products.
The supply of oxygen to a plant is thus seen to be as directly connected with the utilization of the energy of a cell as is that of food concerned in its nutrition.
These include cell walls and the various stored products found in growing cells.
This is evident from the consideration that the growth of the cells is attended by the growth in surface of the cell wall, and as the latter is a secretion from the protoplasm, such a decomposition cannot readily take place unless oxygen is admitted to it.
There is set up at once a certain hydrostatic pressure, due to the turgidity which ensues upon such absorption, and the extensible cell wall stretches, at first in all directions.
The growth or increase of the protoplasm at the expense of the nutritive matter for a time keeps pace with the increased size of the cell, but by and by it becomes vacuolated as more and more water is attracted into the interior.
The growth of the protoplasm, though considerable, is therefore not commensurate with the increase in the size of the cell.
The stretching of the cell wall by the hydrostatic pressure is fixed by a secretion of new particles and their deposition upon the original wall, which as it becomes slightly thicker is capable of still greater extension, much in the same way as a thick band of indiarubber is capable of undergoing greater stretching than a thin one.
The increase in surface of the cell wall is thus duefirstly to the stretching caused by turgidity, and secondly to the formation and deposition of new substance upon the old.
When the limit of extensibility is reached the cell wall increases in thickness from the continuation of the latter of the two processes.
The rate of growth of a cell varies gradually throughout its course; it begins slowly, increases to a maximum, and then becomes slower till it stops.
This may possibly be the cell sap in their interior, which must exercise a slightly different hydrostatic pressure on the basal and, the lateral walls of the cells.
Many experiments point to certain small grains of starch which are capable of displacement as the position of the cell is altered.
The peculiarity of the protoplasm in almost every cell is that it is especially active in the regulation of its permeability by water.
It is the immediate cause of the phenomena of circumnutation, each cell of the circumnutating organ showing a rhythmic enlargement and decrease of its dimensions, due to the admission of more and less water into its interior.
Pythium in seedlingsor to a poison diffusing from cell to cell; in the case of unicellular plantse.g.
Plcotrachelus causes the invaded Pilobolus to swell up, and changes the whole course of its cell metabolism, and similarly with Plasmodiophora in the roots of turnips, and many other cases.
If such a general parasite carries its activities farther, every cell may be killed and the plant forthwith destroyed e.g.
If the attack of a parasite is met by the formation of some substance in the protoplasm which is chemo- tactically repulsive to the invader, it may be totally incapable of penetrating the cell, even though equipped with a whole armoury of cytases, diastatic and other enzymes, and poisons which would easily overcome the more passive resistances offered by mere cell-walls and cell-contents of other plants, the protoplasm of which forms bodies chemotactically attractive to the Fungus.
But even when inside it does not follow that the Fungus can kill the cell, and many cases are known where the Fungus can break throtigh the cells first lines of defence (cell-wall and protoplasmic lining); but the struggle goes on at close quarters, and various degrees of hypertrophy, accumulation of plastic bodies or secretions, discolorations, &c.,, indicate the suffering of the still living cell.
Finally, cases occur where the invaded cell so adapts itself to the presence of the intruder that life in commonsymbiosisresults.
The elementary unit of plant structure, as of animal structure, is the cell.
The Cell Theory.For a general and historical account of the cell theory see CYTOLOGY.
The nucleus was definitely recognized in the plant cell by Robert Brown in 1831, but its presence had been previously indicated by various observers and it had been seen by Fontana in some animal cells as early as 1781.
The cell theory so far as it relates to plants was established by Schleiden in 1838.
He showed that all the organs of plants are built up of cells, that the plant embryo originates from a single cell, and that the physiological activities of the plant are dependent upon the individual activities of these vital units.
It is true that in the unicellular plants all the vital activities are performed by a single cell, but in the multicellular plants there is a more or less highly developed differentiation of physiological activity giving rise to different tissues or groups of cells, each with a special function.
The cell in such a division of labor cannot therefore be regarded as an independent unit.
The simplest cell forms are found in embryonic tissues, in.
The protoplasm of a living cell con.sists of a semifluid granular substance, called the cytoplasm, one or more nuclei, and sometimes centrosomes and plastids.
Very little is known of the finer structure of the cytoplasm of a vegetable cell.
In other forms such as Elodea, Nitella, Chara, &c., where the cytoplasm is mainly restricted to the periphery of the sap vacuole and lining the cell wall, the streaming movement is exhibited in one direction only.
In some cases both the nucleus and the chromatophores may be carried along in the rotating stream, but in others, such as T.Titeila, the chloroplasts may remain motionless iii a non-motile layer of the cytoplasm in direct contact with the cell wall.i Desmids, Diatoms and Oscillaria show creeping movements probably due to the secretion of slime by the cells; the swarmspores and plasmodium of the Myxomycetes exhibit amoehoid movements; and the motile spores of Fungi and Algae, the spermatozoids of mosses, ferns, &c., move by means of delicate prolongations, cilia or flagella cf the protoplast.
They are spherical, oval, fusiform, or rod-like, and are always found in the cytoplasm, never in the cell-sap. They appear to be permanent organs of the cell, and are transmitted from one cell to another by division.
The cell sap contains various substances in solution such as sugars, inulin, alkaloids, glucosides, organic acids and various inorganic salts.
It is probable that most, if not all, the metabolic changes which take place in a cell, such as the transformation of starch, proteids, sugar, cellulose; and the decomposition -of numerous other organic substances which would otherwise require a high temperature or powerful reagents is also due to their activity.
If it is absent, the cell loses its power of assimilation and growth, and soon dies.
HaberIandt has shown that in plant cells, when any new formation of membrane is to take place in a given spot, the nucleus is found in its immediate vicinity; and Klebs found that only that portion of the protoplasm of a cell which contains the nucleus is capable of forming a cell-wall; whilst Townsend has further shown that if the non-nucleated mass is connected by strands of protoplasm to the nucleated mass, either of the same cell or of a neighboring cell, it retains the power of forming a cell-membrane.
This has a strong attraction for basic aniline dyes, and can usually be distinguished from other parts of the cell which are more easily colored by acid anilines.
In multinucleate cells the division of the nucleus is independent of the division of the cell.
It may also take place where rapid proliferation of the cell is going on, as in the budding of the Yeast plant.
The spindle figure is probably the expression of forces which are set up in the cell for the purpose of causing the separation of the daughter chromosomes.
Hartog has endeavoured to show that it can only he formed by a dual force, analagous to that of magnetism, the spindle-fibi es being comparable to the lines of force in a magnetic field and possibly due to electrical differences in the cell.
It is clear, however, that an equal quantitative division and distribution of the chromatin to the daughter cells is brought about; and if, as has been suggested, the chromatin consists of minute particles or units which are the carriers of the hereditary characteristics, the nuclear division also probably results in the equal division and distribution of one half of each of these units to each daughter cell.
The two divisions of the spore mother cell in which the reduction takes place, follow each other very rapidly and are known as Heterotype and Homotype (Flemming), or according to the terminology of Farmer and Moore (1905) as the meiotic phase.
Cell Division.With the exception of a few plants among the Thallophytes, which consist of a single multinucleate cell, Caulerpa, Vaucheria, &c., the division of the nucleus is followed by the division of the cell either at once, in uninucleate cells, or after a certain number of nuclear divisions, in multinucleate cells.
In the Thallophytes the cytoplasm may be segmented by constriction, due to the in-growth of a new cell wall from the old one, as in Spirogyra and Cladophora, or by the formation of cleavage furrows in which the new cell-wall is secreted, as occurs in the formation of the spores in many Algae and Fungi.
In a few cases both among the higher and the lower plants, of which the formation of spores in the ascus is a typical example, new cells are formed by the aggregation of portions of the cytoplasm around the nuclei which become delimited from the rest of the cell iontents by a membrane.
Cell Membrane.The membrane which surrounds the protoplasts in the majority of plants is typically composed of cellulose, together with a number of other substances which are known as pectic compounds.
These layers arc secreted by the protoplasm by the direct apposition of substances on those already in existence; and they may go on increasing in thickness, both by apposition and by the intussusception of particles probably carried in through the protoplasmic fibres, which penetrate the cell-wall as long as the cell lives.
Besides the internal or centripetal growth, some cell-walls are thickened on the outside, such as pollen grains, oospores of Fungi, cells of Peridineae, &c. This centrifugal growth must apparently take place by the activity of protoplasm external to the cell.
In many of the Fungi the non-motile male cell or nucleus is carried by means of a fertilizing tube actually into the interior of the egg-cell, and is extruded through the apex in close proximity to the egg nucleus.
In the Florideae, Lichens and Laboulbenjaceae the, male cell is a non-motile spermatium, which is carried to the female organ.
In Monoblepliaris, one of the lower Fungi, in some Algae, in the Vascular Cryptograms, in Cycads (Zamia and Cycas), and in Ginkgo, an isolated genus of Gymnosperms, the male cell is a motile spermatozoid with two or more cilia.
In the Algae, such as Fucus, Volvox, Oedogonium, Bulbochaete, and in the Fungus Monoblepharis, the spermatozoid is a small oval or elongate cell containing nucleus, cytoplasm and sometimes plastids.
Belajeff regards it as a true centrosome; but this is doubtful, for while in some cases it appears to be connected with the division of the cell, in others it is independent of it.
The eggcell or oosphere is a large cell containing a single large nucleus, and in the green plants the rudiments of plastids.
In plants with multinucleate cells, such as Albugo, Peronospora and Vaucheria, it is usually a uninucleate cell differentiated by separation of the nuclei from a multinucleate cell, but in Albugo bliti it is multinucleate, and in Sphaero plea it may contain more than one nucleus.
The strongest direct evidence seems to be that the nuclear substances are the only parts of the cells which are always equivalent in quantity, and that in the higher plants and animals the male organ or spermatozoid is composed almost entirely of the nucleus, and that the male nucleus is carried into the female cell without a particle of cytoplasm.i Since, however, the nucleus of the female cell is always accompanied by a larger or smaller quantity of cytoplasm, and that in a large majority of the power plants and animals the male cell also contains cytoplasm, it cannot yet be definitely stated that the cytoplasm does not play some part in the process.
Boveri in fact has put forward the view that the chromosomes are elementary units which maintain an organic continuity and independent existence in the cell.
In the Cyanophyceae the contents of the cell are differentiated into a central colorless region, and a peripheral layer containing the chlorophyll and other coloring matters together with granules of a reserve substance called cyanophycin.
In the yeast cell the nucleus is represented by a homogenous granule, probably of a nucleolar nature, surrounded and perhaps to some extent impregnated by chromatin and closely connected with a vacuole which often has chromatin at its periphery, and contains one or more volutin granules which appear to consist of nucleic acid in combination with an unknown base.
The sieve tubes contain a thin lining layer of protoplasm on their walls, but no nuclei, and the cell sap contains albuminous substances which are coagulable by heat.
Protoplasmic Continuity.Except in the unicellular plants the cell is not an independent unit.
He took up his residence in Avila, where he had built a convent; and here he resumed the common life of a friar, leaving his cell in October 1497 to visit, at Salamanca, the dying infante, Don Juan, and to comfort the sovereigns in their parental distress.
The pupal stage is passed in an earthen cell, just beneath the surface of the ground.
All that do not happen to attach themselves to a bee of the genus Anthophora perish, but those that succeed in reaching the right host are carried to the nest, and as the bee lays an egg in the cell the triungulin slips off her body on to the egg, which floats on the surface of the honey.
The violent personalities of a pamphlet entitled Marie Joseph Chenier et le prince des critiques (1844), in reply to Jules Janin, brought him a six months' sojourn in La Pelagic, in the cell just quitted by Lamennais.
Vezhdovsky's figures of Rhynchelmis agree with those of Bergh in showing the backward growth of the nephridium from the funnel cell.
Rarely the nephridium does not communicate with the coelom; in such cases the nephridium ends in a single cell, like the "flame cell" of a Platyhelminth worm, in which there is a lumen blocked at the coelomic end by a tuft of fine cilia projecting into the lumen.
In any case the nephridia which occupy the segments of the body generally are first of all represented by paired structures, the "pronephridia," in which the funnel is composed of but one cell, which is flagellate.
Each renal organ is a sac lined with glandular epithelium (ciliated cell, with concretions) communicating with the exterior by its papilla, and by ce, Cerebral ganglia.
Facing the castle, on the western side of the pill, stand the considerable remains of Monkton Priory, a Benediction house founded by Earl William Marshal as a cell to the abbey of Seez or Sayes in Normandy, but under Henry VI.
Further incursions made by the Danes in 998 and in 1015 under Canute probably resulted in the destruction of the priory, on the site of which a later house was founded in the 12th century as a cell of the Norman abbey of Lysa, and in the decayed condition of Wareham in 1086, when 203 houses were ruined or waste, the result of misfortune, poverty and fire.
During his stay at Manresa, he lived for the most part in a cell at the Dominican convent; and here, evidently, he had severe illnesses.
Klaproth in 1799, is obtained when pure carbon (graphite or charcoal) is oxidized by alkaline permanganate, or when carbon forms the positive pole in an electrolytic cell (Ber., 1883, 16, p. 1209).
Externally is a thin cuticle; this covers the epidermis, which consists of a syncytium with no cell limits.
The most interesting room in the palace is Philip II.'s cell, from which through an opening in the wall he could see the celebration of mass while too ill to leave his bed.
Volta's cell consists essentially of two plates of different metals, such as zinc and copper, connected by an electrolyte such as a solution of salt or acid.
The electromotive force of Volta's simple cell falls off rapidly when the cell is used, and this phenomenon was shown to be due to the accumulation at the metal plates of the products of chemical changes in the cell itself.
Constant cells may be divided into two groups, according as their action is chemical (as in the bichromate cell, where the hydrogen is converted into water by an oxidizing agent placed in a porous pot round the carbon plate) or electrochemical (as in Daniell's cell, where a copper plate is surrounded by a solution of copper sulphate, and the hydrogen, instead of being liberated, replaces copper, which is deposited on the plate from the solution).
He found that the amounts of the substances liberated in each cell were proportional to the chemical equivalent weights of those substances.
In order that the current should be maintained, and the electromotive force of the cell remain constant during action, it is necessary to ensure that the changes in the cell, chemical or other, which produce the current, should neither destroy the difference between the electrodes, nor coat either electrode with a non-conducting layer through which the current cannot pass.
As an example of a fairly constant cell we may take that of Daniell, which consists of the electrical arrangement - zinc zinc sulphate solution copper sulphate solution copper, - the two solutions being usually separated by a pot of porous earthenware.
When the zinc and copper plates are connected through a wire, a current flows, the conventionally positive electricity passing from copper to zinc in the wire and from zinc to copper in the cell.