448 BOTANICAL GAZETTE [DECEMBER 
difference between the progenies resulting from self-pollination and 
those resulting from pollination with f. typica. In other words, 
mut. formosa is dominant over f. typica if it enters the cross as 
a female gamete, but is not even dominant over the weak 
mut. sefacea when the formosa gamete is male. The scheme of 
heredity is: 
mut. formosa X mut. formosa —> mut. formosa 
mut. formosaX{. typica —> mut. formosa 
f. typicaX mut. formosa —> f. typica 
It would have been instructive to cross mut. formosa recipro- 
cally with f. typica from a non-mass mutant strain. (Such crosses 
have been made this year and will be grown next year.) From the 
data at hand, concerning only crosses within the mass mutant 
strain, it appears clear that the external features of all the char- 
acteristic mutations are determined by the female gametes. The 
female and male gametes are not equivalent. Thus, the progeny 
obtained from f. typica, Lex. E-5-229, by pollination with mut. 
formosa is not significantly different from the progeny obtained by 
self-pollination (cf. tables III and VI). The characteristic muta- 
tions occur with their usual frequency regardless of which pollen 
is used. We know that this particular individual of f. typica gave 
about 1 per cent mut. formosa when grown in large cultures from 
self-pollinated seeds. That pollination with pollen of mut. formosa 
does not increase the proportion of this mutation in the progeny 
is strikingly shown by the absence of even a single individual among 
the 133 plants of the cross. In a culture of this size from self- 
pollinated seed the chances are about even that an individual 
of mut. formosa, with a frequency of 1 per cent, would or would 
not turn up. If the use of formosa pollen had appreciably increased 
the frequency of this form in the progeny, a culture of 133 plants 
might have been expected to show it. The results can be inter- 
preted in only one way, that is, the female gamete carries all the 
factors which determine the visible characters of the several forms, 
not only of the 4 mutations, but of f. typica as well. 
Both parent plants of mut. formosa showed a high degree of 
mutability themselves, and gave rise to the other 3 characteristic 
