244) THE STRUCTURE OF FLOWERS. 



the more conspicuous the more masculine is the flower, 

 and the more attractive will it be — one with another, would 

 not therefore be so advantageous as crossing the more female 

 plants with the conspicuous. The former, too, produce 

 relatively more offspring, and might tend to oust the others, 

 and reproduce both the "more masculine" and the "more 

 female " sorts. Intercrossing, therefore, coupled with en- 

 vironing conditions, may together bring about dicecism, as 

 in Strawberries. As this reasoning is rather deduclive, it 

 must be only considered as a suggestion. 



Sexuality and Heterostilism. — This undoubtedly is 

 another source of diclinism, as already alluded to. Mr. 

 Darwin alludes * to Goprosma and Mitchella as indicating 

 this fact. " Coprosma is dioecious, and in the male flowers 

 the stamens are exserted, and in the female flowers the 

 stigmas-, so that, judging from the affinities of these genera, 

 it seems probable that an ancient short-styled fonn, beai-ing 

 long stamens with large anthers and large pollen-grains (as 

 in the ease of several Bubiaceous genera), has been converted 

 into the male Coprosma; and that an ancient long-styled 

 form, with short stamens, small anthers, and small pollen- 

 grains, has been converted into the female form. According 

 to Mr. Meeban,t Mitchella repens is dioecious in some 

 districts ; for he says that ore form has small sessile anthers 

 without a trace of pollen, ihe pistil being perfect ; while in 

 another form the stamens are perfect and the pistil rudi- 

 mentary. Mitchella, therefore, would seem to be heterostyled 

 in one district and dioecious in another," and this can 

 scarcely be due to anything but environment. 



* Forms of Flou'ers, etc., p. 285. See also above, p. 228. 



t Proc. Acad, of Sci. of Philadelphia, July 28, 1868, p. 183. I do not 

 gather from Mr. Meehan's account that he found any difCerence as to 

 locality. Dicecism appears to be a constant character. 



