SECT. II. 



CONIERVACE^E. 



207 



plants, usually of a green colour, growing in fresh and 

 salt water, on moist ground, wet rocks, and thermal 

 springs. There is scarcely a gently running stream in 

 which they may not be seen, like bunches of green 

 threads, attached to stones and waving in the current ; 

 some are so soft as to become almost a mass of jelly 

 when taken out of the water. They are sometimes 

 branched, but more frequently simple, formed of cylia* 

 drical cells, joined in a single 

 long row by their flat ends, and 

 they increase in length by the 

 bisection of their terminal cells. l 



In unicellular plants bisec- 

 tion is an act of reproduction ; 

 in the multicellular Confervse 

 it is an act of growth and ex- 

 tension which is accomplished 

 as follows : The terminal cell 

 of the plant grows to twice its 

 length, the matter within the 

 primordial cell spontaneously 

 divides into two equal parts, 

 and both the film and cellulose 

 coat which cover it, bend round, 

 and form a double layer or cel- 

 lulose division between them. 

 This cellulose layer extends 

 over the whole exterior of 

 the primordial cell, so that the new cellulose division 

 or septum becomes continuous with a new layer which 

 is formed throughout the interior of the cellulose wall of 

 the original cell. In this manner two perfect cells are 

 formed out of one, and as the extreme cell may under- 

 go the same process, the growth of the plant may be 

 continued indefinitely. Branches are sometimes formed 

 by buds springing from any part of the stem ; though 



17 - Ce U multiplication in Con- 

 ferva glomerata :-A, portion of 

 filament with incomplete separa- 

 tion at a, complete partition at b ; 

 B > the separation completed : c, 

 formation of additional layere of 



