20 



BOTANICAL GAZETTE 



[JANUARY 



I made a series of crosses in order to study the nature of this 

 latent mutation of O. blandina. They led to the discovery of some 

 points which seem to deserve a more thorough study than I could 

 give them until now. 



In the first place, it is to be expected that in crosses with those 

 species which do not produce such empty seeds the high figures of 

 both parents will simply be repeated. I tried these cases, deter- 

 mining the amount of normally developed germs in lots of 200 seeds 

 each, after the method already described. I made the crosses in 

 1914 and 1915, and in most cases in both the reciprocal directions. 

 The seeds were taken from 5 successive fruits, and carefully pre- 

 pared so as not to lose any small grains. The results are given 



in table I. 



TABLE I 



Cross 



Percentage of germs* 



Cross 



Cross 



Reciprocal 



O. biennis Xblandina 



O. biennis Chicago X " 



0. Cockereili X " 



0. Hookeri X " 



O. syrticola X " 



99 



95 



99 

 94 

 87 



89 



95 

 91 



83 



91 

 94 



87 



* The dash ( — ) means that the cross has not been tried. 



some 



in 191 5 and tried their seeds after self-fertilization. I got almost 

 the same figures: O. blandinaXChicago 86 per cent, 0. HookeriX 

 blandina 97 per cent, and O. syrticolaXblandina 93 per cent. 



In trials with other species the hereditary property of O. 



na of making germs in only one-half of its seeds : 

 normal condition of producing almost only norma 

 3 in the same way in crosses with O. blandim 



The 



results are given in table II. 



be expected that those mutants 



<es give high percentages after self-fertilization will do the same 



:heir crosses with the velutina mutant (table III). 



The crosses were made in 1915. O. rubrinervis is the same 



used in my Grupp 



O. erythrina is 



mutant from Lamarckiana, of the type of the hybrid form 

 ista of that book; and 0. deserens is a mutant from 0. rubri- 



t^m 



