FLORA AND SYLVA, 



Sprengel, at the close of the eighteenth 

 century, was the first to recognise that insects 

 were influential in promot- 

 er J^f ec ^ s in? fertilization by "brushing 

 fertilization. ° J & 



pollen from the anthers with 

 various hairy parts of their bodies and con- 

 veying it to the stigmas." " His theory " about 

 flowers and their fertilization by insects, Muller 

 says, " although the first effort in this wide 

 field, would have afforded a satisfactory key to 

 the chief puzzles of the floral world had it not 

 contained a very serious flaw." This " flaw " 

 was that Sprengel did not recognise the superior 

 effect of cross- over self-fertilization. " This 

 omission," Muller continues, " was for several 

 generations fatal to Sprengel's work, which 

 was otherwise well fitted to give a power- 

 ful impetus to further research " (" Fertiliza- 

 tion of Flowers," p. 3). This theory Sprengel 

 never put forward nor advocated. Sprengel 

 was happily free from what Darwin's great 

 contemporary, Professor Sedgwick, calls " the 

 dangerous position of those who view all things 

 through the distorting medium of an hypo- 

 thesis." 



It was left to Darwin to supply Sprengel's 

 supposed defect ! The method by which 

 Darwin was led to adopt this theory has been I 

 described above ; a method which seems to 

 have been exactly adapted to produce results, 

 unconsciously to himself, according to his 

 theories. H. Muller, following in his wake, 

 adopted and advocated Darwin's theory 

 throughout his work on " The Fertilization I 

 of Flowers." The constantly reiterated plea 

 for cross-fertilization, oftentimes on very in- 

 sufficient evidence, detracts greatly from the 

 value of his book. The eminent botanist, 

 Axell, held the opinion in contrast to Dar- 

 win and Muller, that the self-fertilization of 

 flowers under equal conditions, in a state of 

 Nature, was the natural fertilization, and that 

 "the most perfect flowering plants are those 

 which regularly fertilize themselves" (Muller, 

 " Fertilization of Flowers," p. 587). Meehan 

 in like manner advocated, as we have seen in 

 one or two examples given above, views simi- 

 lar to those of Axell. With him, also, other 

 cultivators strongly felt "that a great deal 

 too much had been claimed for the work of 

 insects in plant cultivation" [Garden, vol. x. 



493). Every year that passes is bringing addi- 

 tional natural evidence in favour of Sprengel's 

 standpoint. He can, consequently, " well af- 

 ford to bear a small amount of blame" ("Cross- 

 and Self-Fertilization of Plants," p. 7) for his 

 " flaw"! 



In favour of Sprengel's reservation, and 

 against Darwin's theory, stand the numerous 

 cleistogamic flowers. There 

 Gnawers. 1 " 8 cannot Possibly be any differ- 

 entiation in the constitution 

 in the stamens and pistils of their individual 

 flowers. In these forms, too, all cross-fertiliza- 

 tion is absolutely excluded, and yet they are, 

 as Darwin states, " abundantly productive " 

 (" Form of Flowers," p. 3 1 1) ; " they produce 

 as a general rule as many seeds as the perfect 

 (open) flowers" (/#., p. 338) ; " they never fail 

 to produce a large number of seeds " (/#., p. 

 340) ; they are sometimes more productive 

 than the open flowers on the same plant [ib., 

 pp. 322, 326). These cleistogamic flowers are 

 met with on a multitude of plants, and the 

 number of such plants is constantly being 

 added to ; they, in our opinion, refute cate- 

 gorically Darwin's theory about difference of 

 constitution or " differentiation " being neces- 

 sary for the complete fertility in flowers. 



[Note. — Some writers speak of the fer- 

 tilization of dioecious flowers as "cross-fertili- 

 zation." Cross-fertilization for 



Dioecious suc h cases is a misnomer. In 

 flowers. r ... . 



dioecious fertilization there is 



no substitution of the pollen of a different 

 flower for that of its own flower. It is necessi- 

 tated by Nature's own arrangements that the 

 stamens of one plant should fertilize the stigma 

 of another. There is no " crossing " from the 

 other side.] 



" If the conveyance of pollen," Muller says, 

 " to the stigma by insects is of no greater ad- 

 vantage than the direct contact of the repro- 

 ductive organs in the flower "—which the 

 natural evidence of the cleistogamic flowers 

 unequivocally supports — " then," in Miiller's 

 words, "the preference of the former uncertain 

 method (by insects) to the latter seems un- 

 necessary and capricious, and any theory based 

 thereon falls to the ground " (" Fertilization 

 of Flowers," p. 3). 



A Field Naturalist, M.A. 



