84 WEATHERWAX: GAMETOGENESIS IN ZEA Mays 
duce a food of proper quality for the hybrid embryo. In the 
light of later work on xenia, we should be compelled to infer from 
this that the peculiar endosperm qualities necessary in such cases 
were the dominant characters, since we have no evidence that, ex- 
cept in special cases to be mentioned later, the recessive characters 
of the male are ever effective in the endosperm; they are not visible, 
and there is no future generation in which they might be detected. 
Moreover, in a cross between sweet and starchy varieties, the 
_ former being the female, there is produced a starchy endosperm, 
which is harder to digest than the sweet one that would have 
been produced had the triple fusion not occurred. 
The part played by the maize endosperm, then, is to complicate 
the problem and at the same time act as a check on our solutions. 
Were it not for xenia and the attendant hereditary phenomena, 
the logical disposal of the endosperm would be to call it gameto- 
phytic tissue resulting from a triple vegetative fusion to which no 
great significance could be attached: and this would probably have 
been done long ago had the peculiarities of the maize endosperm 
not been known. But the transmission of hereditary characters 
to this tissue, as illustrated in maize and a few other species, 
strongly suggests its parallelism with the sporophyte and saves us 
from an incorrect explanation of the ques ion. 
HEREDITY OF ENDOSPERM CHARACTERS 
Without committing ourselves as to the most logical interpre- 
tation of the endosperm in general, we may, for the purpose of ex- 
plaining genetic data, adopt the convenient expedient of consid- 
ering the endosperm of maize a monstrous sporophyte, a sort of 
sister of the embryo. It derives a vigorous growth stimulus from 
the triple fusion in which it originates. It passes through a series 
of tissue differentiations, none of which, however, resemble very 
closely those characteristic of the embryo. It never reaches 
sexual maturity, and, consequently, has no descendants. Because 
of the sporophytic nature of the endosperm, Mendelian principles 
of heredity have been applied to its study in maize, with results 
unique in many instances, and all dependent, more or less, upon 
the cytological facts here set forth, or, at any rate, nor at variance 
with them. 
