THE ALG^E 



143 



hair, apparently attached to its base. The young antheridium shows a definite 

 apical growth, the segments dividing into a central cell and a series of peripheral 

 cells, the latter dividing into many small cells, each of which produces a single 

 spermatium. The apical cell persists as a large transparent cell (jc) at the apex 

 of the ripe antheridium. 



Procarp. The procarp, also, is formed upon a hair, but this is not usually 

 forked. The procarp develops from the second cell of the hair. This cell 

 divides into a central cell and five peripheral ones. Of the latter, the one turned 

 toward the shoot, i.e. the inner one gives rise to a short carpogonial branch, 

 usually of four cells (Fig. 112, B). The two posterior cells undergo but little 



A 



FIG. 112. A-C, Polysiphonia sp. A, very young procarp (optical section) (x 500). 

 B, two sections of an older procarp : I, medium section ; //, superficial cells ; 

 c, carpogonial cell ; x, auxiliary cell ; s, central cell of the joint. C, fertilized 

 procarp (optical section). D, Callithamnion corymbosum; procarp with two 

 auxiliary cells, x, and long trichogyne. E, fertilized procarp, the auxiliary cells 

 beginning to develop the spores, sp. (D, E, after OLTMANNS.) 



change, and help to form the wall of the cystocarp, which owes its greater part 

 to the two lateral pericentral cells from which arise two lobes, something like a 

 bivalve shell, and completely enclosing the carpogonial branch, except for the 

 long trichogyne. The auxiliary cell (a;) arises by a transverse division from the 

 cell from which the carpogonial branch grows. After fertilization a small cell is 

 cut off from the carpogonium, which fuses with the auxiliary cell, this later fus- 

 ing with the neighboring cells forming a large ccenocyte or multinucleate cell. 

 The latter occupies the centre of the young spore-fruit, and from it the large 

 pear-shaped spores are budded off. The wall of the cystocarp finally forms an 

 urn-shaped envelope enclosing the spores (Fig. 113). The development of the 

 sporocarp in Rhodymenia is very similar. 



