The stereom is furnished either by cortical cells or by the tracheal elements, in a few cases by fibres which arc probably homologous with sievetubes.
E, epidermis; q, phellogen; 1, cells, and ~1, the pheliogen of the lenticel; k, cortical parenchyma, containing chlorophyll.
From the outer cortical myceliuni, again, branches pass through the epidermis and grow out in the soil, In stich cases the roots of the plants are usuall) found spreading in soils which contain a large amount of humus, or decaying vegetable matter.
The food so absorbed passes to the outer cortical mycellum, and from this tc the inner hyphae, which appear to be the organs of the interchangi of substance, for they are attracted to the neighborhood of thi nuclei of the cells, which they enter, and iii which they form agglom erations of interwoven filaments.
If a clean cut remains clean, the cambium and cortical tissues soon form callus over it, and in this callusregenerative tissuenew wood, &c., soon forms, and if the wound was a small one, no trace is visible after a few years.
The cortical tissues gradually shrink and dry up, turning brown and black in patches or all over, and when at length the cambium and medullary ray tissues dry up the whole twig dies off.
Latex, though chiefly secreted in vessels or small sacs which reside in the cortical tissue between the outer bark and the wood is also found in the leaves and sometimes in the roots or bulbs.
The cerebral cortex, and, more definitely, the cortical elements (nerve cells), formed the seat of the activity of the soul, and were ordered into departments according to various functions.
The exciting cause of the hypertrophy, in the case of the typical galls, appears to be a minute quantity of some irritating fluid, or virus, secreted by the female insect, and deposited with her egg in the puncture made by her ovipositor in the cortical or foliaceous parts of plants.
By the fusion of the hyphae in the middle of the mycelium a pseudo-parenchymatous cortical layer has begun to form.
The typical heteromerous thallus shows on section a peripheral, thin and therefore transparent, layer, the cortical layer, and centrally a mass of denser tissue the so-called medullary layer, between these two layers is the algal zone or gonidial layer (figs.
The term epithallus is sometimes applied to the superficial dense portion of the cortical layer and the term hypothallus to the layer, when specially modified, in immediate contact with the substratum; the hypothallus is usually dark or blackish.
The cortical layer is usually more developed on the side towards the light, while in many lichens this is the only side provided with a cortical layer.
The podetia of some species of Cladonia possess no cortical layer at all.
The surface of the thallus often exhibits outgrowths in the form of warts, hairs, &c. The medullary layer, which usually forms the main part of the thallus, is distinguished from the cortical layer by its looser consistence and the presence in it of numerous, large, air-containing spaces.
Which carries with it r, Cortical layer.
A, Upper cortical layer.
D, Lower cortical layer.
If the cortical layer should exhibit positive reaction and the medulla of the same species a negative reaction with both reagents, the result is represented thus, K CaCI i.
An epidermis-like or cortical protective outer layer is very common, and is usually characterized by the close septation of the densely interwoven hyphae and the thickening and dark colour of their outer walls (sclerotia, Xylaria, &c.).
Every leaf originates as a simple cellular papilla (fig 1), which consists of a development from the cortical layers covered by epidermis; and as growth proceeds, the fibro-vascular bundles of the stem are continued outwards, and finally expand and terminate in the leaf.
Ziehen has noted exaltation of the jerk to follow extirpation of a cortical centre.
It will be noted from it that there is no direct relation between the extent of a cortical area and the mass of muscles which it controls.
The mass of muscles in the trunk is greater than in the leg, and in the leg is greater than in the arm, and in the arm is many times greater than in the face and head; yet for the last the cortical area is the most extensive of all, and for the first-named is the least extensive of all.
In the diagram there is indicated the situation of the cortical centres for movement of the vocal cords.
Heidenhain's view is that the cortical centres of the hemisphere are inhibited by peculiar conditions attaching to the initiatory sense stimuli.
C, Cortical bundles.
Most of these cortical bundles are collateral in structure, but in some the xylem and phloem are concentrically arranged; the secondary origin of these bundles from procambium-strands was described by Mettenius in his classical paper of 1860.
A common phenomenon in cycads is the production of roots which grow upwards (apogeotropic), and appear as coralline branched structures above the level of the ground; some of the cortical cells of these roots are hypertrophied, and contain numerous filaments of blue-green Algae (Nostocaceae), which live as endoparasites in the cell-cavities.
A striking feature in the roots of several genera, excluding the Abietineae, is the occurrence of thick and somewhat irregular bands ofthickening on the cell-walls of the cortical layer next to the endodermis.
Each hair is composed usually of a cellular pithy internal portion, containing much air, and a denser or more horny external or cortical part.
In the cortical tissue beneatJI each furrow a wide intercellular space is present running the length of the internode, and called the (C, D, E from Strasburger's Lehrbuch der Bolanik, by permission of Gustav Fischer.) FIG.
Con.) green assimilating cortical branches, which are the ends of branches from the medulla and fit tightly together, forming the continuous surface of the plant.
In all cases, while the internal threads which bear the cortical branches consist of elongated cells with few chromatophores, and no doubt serve mainly for conduction of food substances, the superficial cells of the branches themselves are packed with chromatophores and form the chief assimilating tissue of the plant.
In the bulky forms colorless branches frequently grow out from some of the cortical cells, and, pushing among the already-formed threads in a longitudinal direction, serve to strengthen the thallus by weaving its original threads together.
In the leafy shoot this function is mainly localized in the cortical tissue of the leaves, known as mesophyll, Mesophyli.
In some cases where there is apparently a well-marked plerome at the apex, this is really the young pith, the distinction between the stelar and cortical initials, if it exists, being, as is so often the case, impossible to make out.