LIFE HISTORIES OF ALG^E 24! 
OUTLINE OF LIFE HISTORY OF ASCOPHYLLUM 
Spermagonial-plant Oogonial-plant 
(Sporophyte) (Sporophyte) 
4- 4- 4- 4- 
Spermagonium Oogoniun 
(Sporangium) (Sporangium) 
I 4, -I i 
Protoplast of spermagonium Protoplast of oogonium 
(spore-mother-cell) (spore-mother-cell) 
4- 4- 4- Reduction "*' 
Spore Spore Spore Spore Spore Spore Spore Spore 
4, 4- 
64 sperms 8 less 4 eggs 
(Reduced male gametophyte) (Reduced female gametophyte) 
Oosperms (rest) 
vr ~*~ * '4' 
Spermagonial-plants Oogonial-plants 
(Sporophytes) (Sporophytes) 
226. The Cause of Sex. One of the many very inter- 
esting things revealed by a study of the life history of 
Ascophyllum nodosum is the fact that part of the fertilized 
eggs give rise to plants that bear only male gametes, and 
the remainder to plants that bear only female gametes. 
Since the fundamentally different individuals develop 
under identically the same environmental influences, we 
are forced to the inference that the difference lies in the 
fertilized eggs themselves. Some of them appear to be 
male-producing, others female-producing. In what does 
this fundamental difference consist? Here is a very 
important problem, but further consideration of it must 
be postponed until Chapter XXII. 
16 
