File:EB1911 Plants - examples of cell differentiation.jpg

English: Examples of the differentiation of the cells of plants.

A, Cell (individual) of the unicellular Green Alga Pleurococcus, as an example of an undifferentiated autonomous assimilating cell. pr., Cell protoplasm; n., nucleus; chl., chloroplast; c.w., cell-wall.

B, Plant of the primitive Siphoneous Green Alga Protosiphon botryoides. The primitive cell sends colourless tubelets (rhizoids, rh.) into the mud on which it grows. The subaerial part is tubular or ovoid, and contains the chloroplast (chl.). There are several nuclei.

C, Base of the multicellular filamentous Green Alga Chaetomorpha aerea. 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.

D, Part of branched filamentous thallus of the multicellular Green Alga Oedocladium. cr. ax, Green axis creeping on the surface of damp soil; rh., colourless rhizoids penetrating the soil; asc. ax., ascending axes of green cells.

E, Vertical section of frond of the complicated Siphoneous Green Alga Halimeda. The substance of the frond is made up by a single much-branched tube, with interwoven branches. cond med., Longitudinally running comparatively colourless central (medullary) branches, which conduct food substances and support the (ass. cor.) green assimilating cortical branches, which are the ends of branches from the medulla and fit tightly together, forming the continuous surface of the plant.

F, Section through the surface tissue of the Brown Alga Cutleria multifida, showing the surface layer of assimilating cells densely packed with phaeoplasts. The layers below have progressively fewer of these, the central cells being quite colourless.

G, Section showing thick-walled cells of the cortex in a Brown Alga (seaweed). Simple pits (p.) enable conduction to take place readily from one to another.

H, Two adyacent cells (leptoids) of a food-conducting strand in Fucus (a Brown seaweed). The wall between them is perforated, giving passage to coarse strands of protoplasm.

I, End of hydroid of the thalloid Liverwort Blyttia, showing the thick lignified wall penetrated by simple pits.