448 BOTANICAL GAZETTE [December 



difference between the progenies resulting from self-pollination and 

 those resulting from pollination with f. typica. In other words, 

 mut. Jormosa is dominant over f . typica if it enters the cross as 

 a female gamete, but is not even dominant over the weak 

 mut. setacea when the formosa gamete is male. The scheme of 

 heredity is: 



rant. formosaX'omt. formosa -> amt. formosa 

 rant. formosaXi. typica -> mut. formosa 

 f. typicaXmut. 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 I per cent mut. formosa when grown in large cultures from 

 self-poHinated seeds. That polUnation 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 i per cent, would or would 

 not turn up. If the use oi 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 

 mutabihty themselves, and gave rise to the other 3 characteristic 



