150 The Ottawa Naturalist. [Feb. 



entirely unfertilized."^ The hybrid V. fimbriatula x sororia, 

 according to Dr. Brainerd, is less sterile than most hybrids, 

 but never was a capsule found that contained more than half 

 the normal number of seeds.® Also in other hybrids, the char- 

 acteristic sterility of the capsules is most typical. Thus, V. 

 cucuUata x septentrionalis was found to bear onl}^ from one to 

 six seeds'' and, in the hybrid V. septentrionalis x sororia, "the 

 uniformly stunted and often distorted capsules containing 

 mostly aborted ovules"® clearly betrayed its mongrel origin. 

 In V. affinis x sororia the capsules of the cleistogamous flowers 

 were found to be small and often one-sided and relatively 

 infertile" and in V. cucuUata x sororia although numerous, 

 proved to be all small, imperfect and few seeded.'"" 



The above quotation will suffice to substantiate what was 

 stated without confirming evidence on a previous page, namely, 

 that in a hybrid between two violet species, the faculty of 

 producing the normal amount of germinable seed is most con- 

 spicuously reduced. To avoid misconception, it ma}'' be 

 pointed out, especially, that the degeneration of the sexual 

 organs mentioned above refers to the cleistogamous flowers, 

 that is to say the flowers, which in specimens belonging to a 

 " good " species normally produce an abundance of well developed 

 seed. As the cleistogamous flowers are always self-fertilized 

 this failure, in hybrid plants, to bear seed of normal reproductive 

 vigour, cannot be explained by assuming that the pollen neces- 

 sary for the fertilization of the ovules has not been available. 

 It can be explained only by recognizing the fact that the mixing 

 of and unnatural union of sexual units, belonging to distinct 

 species, in the reproductive organs of the hybrids, is causing 

 a disturbance of the functions of the sexual cells which mani- 

 fests itself in partial or total sterility. 



The inability of the cleistogamous flowers of hybrid plants 

 to produce seed of normal vitality is thus very pronounced. 

 This being the case, it is evident that when violet plants are 

 found having sterile cleistogamous flowers they may be looked 

 upon as possible hybrids. In fact, such plants in most cases 

 are really hybrids. The sterility of the capsules of the 

 cleistogamous flowers in violets is therefore a character which 

 will prove most helpful for the identification of critical forms as 

 hybrids. 

 ^ I.e. 217 

 « I.e. 218 

 ' I.e. 220 



8 I.e. 221 



9 I.e. 222 

 " I.e. 222 t 



(To be continued) 



