416 BOTANICAL GAZETTE [NOVEMBER 
that degenerations in the stamens and ovules are “caused by the 
inherent tendency in the species to become dioecious.”’ ‘‘ Faulty 
nutrition”’ is so indefinite and vague, and includes such a wide 
range of possibilities that it can scarcely be considered as an 
adequate explanation. It is more probably a condition which calls 
into greater activity certain fundamental and at present unknown 
causes of degeneration that are always present in a wide range of 
angiosperm forms. It is barely possible that the peculiar detached 
vascular bundle of the ovule may be responsible for the failure of 
the ovule in later stages. This bundle never has been found con- 
nected with the general vascular system of the peduncle, even in 
those infrequent instances when the embryo and endosperm seem 
to be developing normally. If this should prove to be the immedi- 
ate cause for later degenerations in the ovule, there still remains no 
hint of the cause for the failure of the ovular vascular bundle to 
make proper connections. 
STRASBURGER (10) concluded from his study of the species of 
EUALCHEMILLA that sterility is the result of excessive mutation. It 
seems clear that sterility, partial or complete, results from degenera- 
tions, and probably such degenerations are the only morphological 
causes of sterility. It might follow then that excessive mutation 
is the cause of sterility, or it may be that mutating species are only 
more susceptible to degenerations. 
JeFFREY (6) believes that sterility is the result of hybridization. 
Again, it is a question whether hybridity is a fundamental cause, or 
only produces physiological conditions that activate a more or less 
latent tendency to degenerations. If hybridity is the underlying 
cause of the degenerations that lead to sterility, and the theory that 
these degenerations lead to dicliny, apogamy, and the development 
of successful methods of vegetative propagation should prove to be 
correct, it would seem to follow that all hybrids are tending toward 
these states. Probably the evidence would not support this 
reasoning. It is more probable that there exists no causal relation 
between the hybrid state and degenerations, except as physiological 
conditions in hybrids favor such processes. 
Dorsey (2) concludes from a study of grape hybrids that 
“hybridity is not necessarily a cause of sterility,’’ and that “pollen 
