250 Dr. Ida A. Keller on the 



of Sprengel, but rather to develop more fuUj our knowledge 

 of cross-fertilization. I need only refer to the famous work 

 of Darwin, to that of the well-known German botanists 

 Hildebrand, H. Miiller, Kerner, and to that of the many 

 close observers of our own day. 



The fact that cross-fertilization is of utmost value to the 

 individual species has been emphasized by Darwin. In fact 

 this great discoverer contends repeatedly that pollen applied 

 to the pistil of the same flower is a positive injury to the 

 species. It is curious to note how this idea has influenced 

 the authors of botanical text-books. As one instance in 

 many I need only refer to Gray's ' Structural Botany.' To 

 the rather long- chapter devoted to the description of the 

 adaptation of flowers to insure intercrossing a few paragraphs 

 are added in which the writer, it seems to me rather unwil- 

 lingly, admits that there are also special adaptations to insure 

 close fertilization — in fact, that there are cases which posi- 

 tively exclude all chances of a cross. Of cleistogamous 

 flowers Gray says : — " Here the intention and the accom- 

 plishment of self-fertilization are unmistakable. This peculiar 

 dimorphism consists in the production of very small or incon- 

 spicuous and closed flowers, necessarily self-fertilized and 

 fully fertile, in addition to ordinary, conspicuous, and much 

 less fertile, though perfect flowers " *. He then continues : — 

 "It has been said that the ordinary flowers in such plants are 

 sterile, and perhaps they always are so, except when cross- 

 fertilized ; in most cases they are habitually infertile or 

 sparingly fertile. Prohahly they suffice to secure in every 

 few generations such benefit as a cross may give, while the 

 principal increase is by cleistogamous self-fertilization, which 

 thus off'sets the incidental disadvantage of the former mode." 

 1 have quoted the writer verbatim, because the extract shows 

 so plainly his mental attitude in regard to the significance of 

 this phenomenon. Here we have a concession in regard to 

 the extreme fertility of cleistogamous flowers, followed by a 

 suggestion in regard to the few mostly infertile conspicuous 

 flowers which accompany the formei*, and from these and the 

 statement that no species is altogether cleistogamous, taken 

 as a premise, the following conclusion is drawn : — ■" Thus, 

 cleistogamy, with all its special advantage, testifies to the 

 value of intercrossing." The same bias, looking favourably 

 upon cross-fertilization, may be observed in most writers on 

 the subject. The prevailing impression seems to be that close 

 fertilization is, as a rule, only resorted to when all the chances 

 for cross-fertilization are at an end. 



* Gray's ' Structural Botany/ p. 241. 



