THE ALG^E 



107 



In C. scutata the oogonia 



C 



spores are formed singly from any cell of the thallus. 



arise from the end-cells of the 



radiating rows of cells of which 



the thallus is composed. These 



differ but little, except in size, 



from the vegetative cells. In C. 



pulmnata, which has the branches 



free, and forming a cushion-shaped 



mass, the oogonia are free at the 



ends of the branches, and, have 



a long neck, through which the 



spermatozoids enter. 



The antheridia in the disk- 

 shaped forms like C. scutata (Fig. 

 77, C) are formed by the division 

 of a thallus-cell into four small 

 cells, which are colorless, and each 

 of which gives rise to a single 

 biciliate spermatozoid. In C. pul- 

 vinata the antheridia are small 

 oblong cells on the ends of the 

 branches. After fertilization is 

 effected, the egg-cell develops a 

 thick wall, but in addition to this 

 short branches grow out from the 

 cells adjacent to the oogonium, 

 which they envelop with a sort of 

 rind, or cellular envelope, so that 

 a "spore-fruit" is developed, con- 

 sisting of the resting-spore, envel- 

 oped by the sterile protective 

 mantle of cells (Fig. 78, B). 



On germination the spore divides 

 by cell-walls into a globular mass 

 of cells, from each of which a 

 swarm-spore arises. Each swarm- spore gives rise to a new plant. The germi- 

 nation of the spore in Coleochsete resembles closely the same process in the low- 

 est of the Mosses, and in connection with the reproductive organs, as well as the 

 form of the plant, has suggested a possible remote relation between the lower 

 Mosses (Hepaticse) and the Confervoidese. 



FIG. 78. A, branch of Coleochsste pulvinata, 

 with an oogonium, og. B, section of oospore, 

 surrounded by the cortex, r, developed from 

 the adjacent cells. C, section of a germi- 

 nated spore, divided into a mass of cells. 

 (All after OLTMANNS.) 



Classification of Confervoideae (Engler and Prantl, 9) 



A. Isogamce. Gametes alike. 



Families : Ulvacese, Ulothricacese, Chsetophoracese, Mycoi- 



deacese, Cladophoracese, Gomontiacese. 

 -B. Oosporece. Gametes differentiated into non-motile eggs and 



spermatozoids. 



Families: Spheeropleaceae, CylindrocapsaceaD, (Edogouiaceae, 

 Coleochsetaceae. 



