These arise from the axial cell, and are multicellular and branched.
Many Siphonales are encrusted of planes and a multicellular individual.
In these cases, certain cells of a colony of unicellular plants or of the filaments of multicellular plants enlarge greatly and thicken their wall.
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.
In some filamentous forms this " fragmentation " into multicellular pieces of equal length or nearly so is a normal phenomenon, each partial filament repeat s ing the growth, division and q?
The megaspore is filled with tissue as in typical Gymnosperms, and from some of the superficial cells 3 to 5 archegonia are developed, characterized by long multicellular necks.
Such colonial forms as Hydrurus and Phaeocystis are supposed, however, to indicate a stage in the passage to the multicellular condition.
Melobesia callithamnioides gives rise to multicellular propagula; Griffithsia corallina is said to give rise to new individuals, by detaching portions of the thallus from the base of which new attachment organs have already arisen.
In one type they may take the form of specially-modified single epidermal cells or multicellular hairs without any direct connection with the vascular system.
A growth both of the funnel, which becomes multicellular, and of the rest of the nephridium produces the adult nephridia of the genera mentioned.
This very large group of plants is characterized by the possession of a special type of conidiophore - the basidium, which gives its name to the group. The basidium is a unicellular or multicellular structure from which four basidiospores arise as outgrowths; it starts asa binucleate structure, but soon, like the ascus, becomes uninucleate by the fusion of the two nuclei.
In all the multicellular plants of this group which have been adequately investigated, vegetative multiplication by means of what are known as hormogonia has been found to occur.
C, Base of the multicellular filamentous Green Alga Chaetomorpha aes-ea.
D, Part of branched filamentous thallus of the multicellular Green Alga Oedocladium.
Many forms, even when multicellular, have all their cells identical in structure and function, and are often spoken of as physiologically unicellular.
The hairs are multicellular, and of two kinds, one branching and ending in a fine point, while the other, unbranched, terminates in a clump of small cells.
At the present day feiy groups of the animal kingdom are so well known to the microscopist, few groups present more interesting affinities to the morphologist, and few multicellular animals such a low physiological condition.
The protoplasm then becomes cut up by a series of clefts into a number of smaller and smaller pieces which are unicellular in Pilobolus, multicellular in Sporodinia.
The multicellular species consist of filaments, branched or unbranched, which arise by the repeated divisions of the cells in parallel planes, no formation of mucilage occurring in the dividing walls.
Of these the first three include multicellular plants, some of them of great size; the last three are unicellular organisms, with little in common with the rest excepting the possession of a brown colouring matter.
- Lord Kelvin's Multicellular Electrostatic Voltmeter.
Spores unicellular, parallel-multicellular or muriform, usually colourless, cross-walls usually thin.
6, The multicellular ascogonium 3, Passage of the antheridial derived by division from the nucleus towards that of the oogonium; the terminal cell oogonium.
The spores themselves may be unicellular without a septum or multicellular with one or more septa.
- Round Dial Kelvin Multicellular Electrostatic Voltmeter, 5-in.
One of the best known of these is Lord Kelvin's multicellular voltmeter.
Such hyphae may be multicellular, or they may consist of simple tubes with numerous nuclei and no septa (Phycomycetes), and are then non-cellular.