Ii6 



THE ALGAE 



nodes. The nodes are formed by a transverse layer of cells in con- 

 tradistinction to the internodes, which consist of one large cell 

 whose individual length may extend up to 25 cm. in Nitella cernua. 

 The height of the different species varies up to i m., growth being 



Fig. 66 Charales. A, Nitella batrachosperma. B, Char a hispida. C, 

 underground bulbil of C. aspera. D, germinating oospore. E, 

 protonema oiC.fragilis. F, young plant of C. crinita. ap = accessory 

 protonema, i =intemode, p = protonema, r =rhizoids, rn =rhizoid 

 node, s = shoot, 5n =stem node, v = initial of young plant. (After 



Fritsch.) 



brought about by an apical cell which cuts off successive segments 

 parallel to the base. Each new segment divides transversely into 

 two halves, the upper developing into a node and the lower into an 

 internode (Fig. 67). Branches, both primary and secondary, are 

 formed by the peripheral cells of the nodes protruding to form 



