STUDIES IN THE DEVELOPMENT OF THE PIPERACEAE 727 
DISCUSSION 
The most interesting questions raised by the foregoing work 
on Piper betel are those concerning the different degrees of sup- 
pression of sporangia and sporophylls. 
From the progressive series of reductions above noted, it seems 
fair to assume that whatever influence is at work to suppress 
sporangial development, is also concerned with the complete sup- 
pression of the stamens or carpels, and thus determines the for- 
mation of male or female flowers, w^hich in many cases, make up 
the whole spike, to the exclusion of hermaphrodite ones. In 
other words, it is this influence that determines whether gameto- 
phytes of one or both sexes shall be formed at the next step in 
the life cycle of this plant, and of which sex they shall be. 
. We can take up these questions in regard to Piper betel more 
profitably after reviewing what is known of other plants, first 
concerning the time, and second, concerning the immediate cause 
of the differentiation of sexes in gametophyte or sporoph3^te. 
Of well-known forms among the algae it is clear that in Vau- 
cheria, Nemalion and some species of ^pirogyra. GEdogonium, 
Coleochaete and Fucus, the individual plants are distinctly her- 
maphrodite, since the two kinds of sexual cells may arise close 
together on the same plant. In other species of Spirogyra, GEdo- 
gonium, Coleochaete and Fucus and in many Chlorophycese, 
Phaeophyceae and Floridea), the sexual plants bear one kind of 
sexual organs only. 
In such a form as a dioecious species of GEdogonium, e.g., the 
hermaphrodite condition can be supposed to exist, if at all, only 
up to the formation of the zoospores from the zj'^gote. It is not 
known whether all zoospores from one zygote give rise to plants 
of the same sex or not. In dioecious species of Fucus there is no 
evidence to show that the thallus is not unisexual from the time 
of its origin from the oospore. Hence the hermaphrodite condi- 
tion must be supposed to exist in the oospore only, and for a very 
short time. In hermaphrodite species of Fucus we must con- 
ceive of the thallus as being hermaphrodite up to the time of 
differentiation of antheridia and oogonia. If Yamanouchi's ('09) 
