244 
STRUCTURE AND LIFE HISTORIES 
antheridium continues to divide until as many as 1,500 or 
more sperms are formed in each one. Since the antheridia 
occur in groups oisori (Figs. 178 and 179), the total num- 
FIG. 178. Dictyola dichotoma. Cross-section of a male thallus, show- 
ing the comparative development of the antheridial son, and the tufts of 
hairs which are scattered over the frond, a, young sorus; b, older sorus; 
c, sorus opened. The sperms have been set free. There remain only the 
cells which form the involucre, d, tuft of very young hairs; e, tuft of 
older hairs; /, the same fully developed. X about 35. (After Thuret.) 
FIG. 179. Dictyota dichotoma. A, vertical section through portion 
of sorus, showing antheridia; B, sperms. (Redrawn from J. Lloyd Wil- 
liams.) 
her of sperms formed on one plant, or even in one sorus, 
is enormous. The oogonia may occur singly or in groups 
(Fig. 180). 
