s cp 



Fig. 145 Callithamnion. A-G, stages in development of Cystocarp 

 from mature Carpogonium. a = auxiliary cell, cp = carpogonium. 

 s = sporogenous cell cut off from fertilized carpogonium. sc == sup- 

 port cell. H, antheridia with spermatia. I, the same enlarged. J, 

 antheridial sori. K, young tetrasporangium. L, mature tetra- 

 sporangium (A-F, x 520; G, x 300). (A-G, after KyUn; H-J, after 

 Grubb; K, L, schematic after Mathias.) 



Strands are apparently capable of some movement their function is 



obscure. 



The antheridia, which form hemispherical or ellipsoidal tufts on 

 the branches, arise as lateral appendages, the first cell to be cut off 

 being the stalk cell. This stalk cell gives rise to a group of secondary 

 cells which later on divide to form branches composed of two to 

 three cells, each terminating in an antheridial mother cell. In this 

 genus there may be two or even three crops of antheridia arising 

 successively in the same place, each mother cell producing about 

 three antheridia in every crop. The cystocarps, which are usually 

 present in pairs and enclosed in a gelatinous envelope, arise as 



255 



