270 



PART III. THE CLASSIFICATION OF PLANTS. 



The simplest mode of direct formation of the cystocarp occurs 

 in the Bangiaceae ; the cavity of the carpogonium becomes cham- 

 bered, by the formation of cell-walls, into usually eight ceils, each 

 of which is a sporangium, giving rise to a carpospore : only a 

 single spore is formed in the genus Erythrotrichia. In other cases 

 of direct formation (e.g. Nemalion, Batrachosperraum, Chantransia, 

 Lemanea), the carpogonium gives rise to a number of filaments, 

 termed ooblastema-filaments^ which bear a cluster of sporangia 

 (Fig. 194). 



In the indirect formation of the cystocarp, the carpogonium 

 fuses with one or more of the auxiliary cells. In the simplest case 



B. 



FIG. 195. Sexual organs of Spermothnmnion hermfiphrodilum. A Mnle and female organs ; 

 c multicellular procarp; t trichogyne ; t' trichophore ; on terminal cluster of antheridia. 

 B cystocarp developing from the fertilised procarp ; a cluster of carposporangia is 

 springing from each of the two opposite lateral auxiliary cells. The development of tha 

 cystocarp is indirect (x300: after Naegeli). 



(e.g. Gigartinacese, E/hodymeniaceae, Sphserococcese, Rhodomelacea3), 

 the carpogonium fuses directly with the auxiliary cell (or cells), 

 and from the latter the sporangia, or filaments bearing sporangia, 

 are formed. In other cases the carpogonium gives rise to one 

 or more elongated, branched, ooblastema-filaments which fuse 

 with one or more auxiliary cells, and the sporangia are produced 

 either from the ooblastema-filaments (e.g. Gelidiaceae) or from the 

 auxiliary cells (e.g. Squamariacese and other Cryptoneminse). 



In the Corallinacese, where the procarps are aggregated in re- 

 ceptacles, only a single cystocarp is formed from the whole group 

 of procarps. Some of the procarps appear to be altogether abor- 

 tive, and only those toward the centre of the group have tricho- 



