238 THE STRUCTURE OF FLOWERS. 



found that a few warm days in winter would advance the 

 male flowers, so that they would mature some weeks before 

 the female flowers opened. Hence the latter were generally 

 unfertilised.* 



That the stamens are much more sensitive to and pre- 

 cocious in their development under a rise of temperature, is 

 seen in the behaviour of plants in different countries. Thus 

 it is asserted f that Stratiotes aloides produces its carpels 

 with greater abundance towards the northern limit of its 

 geographical distribution, and its stamens, on the contrary, 

 are more frequently developed in more southern districts. J 



These tendencies to check one or the other sex, may lead 

 to monoecious diclinism ; and even complete dioecisin seems, 

 at all events to some extent, due to climate, as differences 

 occur in widely separated countries ; thus HoncJienya peploides 

 is frequently hermaphrodite in America, but usually sub- 

 dioecious in England. § 



Mr. Darwin, in his experiments, found that Mimuhis 

 Itifeus was very sterile in one year ; and he attributed the 

 fact partly to the extreme heat of the season. || 



* Proc. Acad. Nat. Sci. of Phil., 188 i, p. 116. 



t Teratology, p. 196. -^ 



X Perhaps the propagation by apogamy of the female plants of 

 Chara crinita may be a resource to which this plant has been driven in 

 consequence of the male plants not thriving in a cool region. Sachs 

 says tliat the female is found throughout the whole of Northern Europe, 

 but the male is only known to occur in Transylvania, South of France, 

 and by the Caspian (Phys. of Plants, p. 801). 



The idea is suggested by this that when temperature arrests the 

 male without checking the vegetative system, a plant may adopt 

 vegetative methods of multiplication. Thus, instead of regarding the 

 " root-tubers " and aerial corms of Ranunculus Ficaria as the cause of 

 the degeneracy of the pollen in that plant ; perhaps it would be more 

 correct to reverse the process. 



§ Teratology, p. 196. || Cross and Self Fert., etc., p. 68. 



I 



