no 



CHLOROPHYCEAE 



part in determining the production of the sex organs. The species 

 are either dioecious or monoecious, in which latter case the 

 oogonia and antheridia are juxtaposed, the oogonia being directed 

 upwards and the antheridia downwards, both organs usually 

 appearing on secondary lateral branches of limited growth. 



Fig. 75- Charales. A, i-6, successive stages in development of root node of 

 Char a aspera. i, double foot joint. 2, dilation of toe of upper foot. 3, toe portion 

 cut off. 4, 5, subdivision of toe cell. 6, rhizoids growing out. B, 1-3, successive 

 growth stages of apex of Nitella. In i apical cell is undivided, in 2 it has divided, 

 in 3 the lower cell has divided into an upper node and a lower intemode. 

 C, C. hispida, node with stipules. D, A'', gracilis, longitudinal section of node. 

 E, C. fragilis, branch at node with axillary bud. a = antheridium, ac = ascending 

 corticating cells, as = apex of side branch, 6«/ = basal node of branch (I), c and 

 CO = cortical cells, J= descending cortical cells, f = internodal cell, w = nodal cell, 

 = oogonium initial, 5 = stipule. (A, B, after Grove; C-E, after Fritsch.) 



Antheridia. Fig. 76. 



The apical cell of the lateral branch cuts off one or two discoid 

 cells at the base and then becomes spherical. The upper spherical 

 cell divides into octants and this is followed by two periclinal 

 divisions after which the whole enlarges and the eight peripheral 

 cells develop carved plates {shields), thus giving the wall a pseudo- 

 cellular appearance. At maturity these peripheral cells acquire 



