222 ALG^'E 



the cortical layer is then thrown off, and the oosperm divides into several 

 cells or carpospores. The germinating carpospore does not give rise to a 

 new thallus, but to a zoospore, which gives birth to several successive non- 

 sexual generations propagated by zoospores, until the cycle of generations 

 is completed by the production of a sexual individual. 



Mycoidea parasitica Cunn. (Trans. Linn. Soc, vol. i., 1879, P- S^^) 

 is probably nearly allied to Coleochsete, which it resembles in the nature 

 of its thallus and in its mode of reproduction. It is endophytic in the 

 cells of the leaves of Camellia in tropical India, inflicting great injury 

 on the trees. Ward (Trans. Linn. Soc, ii., 1884, p. 87) contends that 

 Mycoidea is in reality an epiphyllous lichen. Mobius (Ber. Deutsch. 

 Bot. Gesell., 1888, p. 242) regards Mycoidea, and the nearly allied 

 Chsetopeltis (Berth.), as more probably belonging to Chcetophoraceae. 



Literature. 



Brebisson — Ann. Sc. Nat., i. , 1844, p. 25. 

 Pringsheim — Jahrb. wiss. Bot., i860, p. i. 

 Kny — Ber. Deutsch. Bot. Gesell., 1884, p. 93. 



Order 2.— CEDOGONiACEyE. 



This small order, as at present constituted, comprises only two 

 genera — CEdogonium (Lk.) and Bulbochaete (Ag.). 



CEdogonitwi includes several species, abundant in streams, ponds, 

 and tanks. They are readily distinguished by the fact that they never 

 branch, by the cells being of small diameter and considerable length, 

 filled with a homogeneous dark-green protoplasm with a parietal nucleus, 

 and by the peculiar appearance of annular striae near one end of some 

 of the cells. These striae result from the appearance known as 'inter- 

 calary surface-growth.' Below the septum is formed an annular deposit 

 or cushion of cellulose ; at this place the cell-wall splits, as if by a 

 circular cut, into two pieces, which separate from one another, but re- 

 main united by a zone of the cell-wall formed by an extension of the 

 cushion. This process is constantly repeated over a short space of the 

 cell-wall immediately beneath a septum, each slit being a little further 

 from the septum than those that preceded it ; so that these pieces, form- 

 ing small projections, give to the upper end of the cell the appearance 

 of consisting of caps placed one over the other ; while its lower end 

 appears as if enclosed in a long sheath consisting of the portion of the 

 cell-wall below the caps. This lower portion of the cell is always cut 

 off by a septum from the upper cap-bearing portion. The filaments 

 are fixed at their base by a rhizoid to solid bodies or submerged plants. 



Non-sexual propagation takes place in CEdogonium by means of 

 zoospores^ the formation of which affords a typical example of the process 



