480 COBB AND BARTlvETT: INHERITANCE IN OENOTHERA 



ence to an earlier paper (see footnote 2). Some progenies con- 

 tain many mutations, and mutability would therefore be de- 

 tected by growing relatively few individuals. Others, on the 

 contrary, contain very few, and a very large progeny indeed 

 would have to be grown in order to feel reasonably sure of the 

 non-mutability of the parent. The authors plan to gather 

 further data bearing on what we may term the "inheritance of 

 mutability" in these crosses between the strains of Oe. pratincola. 

 For the present we shall give only the data contained in Table 6. 

 As far as the results go they are in conformity with expectation. 

 The Fi progenies of crosses between any form of strain C and mut. 

 formosa E resemble the C parent, in that the leaves are all fiat. 

 In the F2 we may or may not detect mutations, since they may 

 occur only among one-quarter of the progeny, those having the 

 factorial composition a/3ff. It is of course always possible for 

 a gametes to undergo mutative modification to the condition de- 

 termining revoluteness, but the mutative modification, if it oc- 

 curs, is masked in plants carrying the factor F, either from one 

 or both parents {i. ^., in 3 out of 4 F2 plants). In case the plant 

 has the constitution a/SFF or o;/3 Ff it can never show revolute- 

 ness ; however the a gametes may become modified. 



THE PRODUCTION OF MUT. NUMMUIvARIA. 



One especially interesting fact is that strain E after having 

 been crossed with strain C gives rise to mut. nummularia. Un- 

 der ordinary circumstances it never does so. Similar phenomena 

 are sometimes viewed as due to metacliny. Metacliny, a term 

 first used by de Vries,^*^ may be explained in the terms of the 

 o;/3 hypothesis as follows: Although most female gametes are 

 a., and most male gametes are /3, there are exceptions to both 

 rules, so that occasionally identical zygotes result from reversed 

 fertilizations, the majority of the zygotes being of the constitu- 

 tion aQ, and only a few Qa. Cases of this sort have been de- 

 scribed by La Rue and Bartlett. Among the mutation crosses 

 of Oe. Reynoldsii. The production of mut. nummularia by 



1' DE Vries, H. Gruppenweise Artbildung, pp. 308-310. 



