CHAP. I.] PLANT ARCHITECTURE. 13 



and green seaweeds. Plants that consist of more than 

 one cell are called multicellular. To the multicellular 

 type belong all flowering plants, ferns, mosses, also 

 many of the funguses and seaweeds. Unicellular plants 

 only occur in the seaweeds [Algce], and the funguses 

 (Fungi). The multicellular type of structure is not entirely 

 new and independent of the more primitive unicellular 

 -type of plant structure, but is in reality only a modifica- 

 tion of the latter type. It will be remembered that in 

 the unicellular organism, the single cell could only be 

 considered as an individual during the vegetative phase, 

 as on entering the second or reproductive condition its 

 own individuality was lost by becoming divided into two 

 parts quite independent of each other and constituting 

 two distinct individuals. This sacrifice of the individual 

 at the termination of the vegetative phase is due to the 

 primitive mode of reproduction by fission. 



Every living body, both plant and animal, consists in 

 the earliest condition of a single cell, and further, the 

 single cell constituting the starting point of the multi- 

 cellular plant divides by fission, forming two cells as in 

 the unicellular type; these two cells do not separate 

 from each other, but remain in organic contact, that is, 

 the separating wall does not split; each cell thus formed 

 again divides, exactly as in Pleurococcus, and thus by the 

 repeated fission of cells that remain in contact, a tissue 

 is formed that takes the form of slender filaments or 

 thin, broadly extending sheets, as already stated in the 

 simpler forms of multicellular plants, and by exactly the 

 same process of cell-division the entire substance of the 

 largest forest tree is built up. 



An early indication of division of labour amongst the 



