258 MON(ECious AND DICECI0U3 PLANTS. [September, 



is opposed to that of M. Lecoq, Avho, in his elaborate work on 

 the ' Botanical Geography of Europe/ says that in Mercurialis 

 annua he has always seen the two sexes mixed in about the same 

 proportions. According to our own experience the female plants 

 of this species are not so commonly met with as the male^ but 

 this is a point on which we should be glad to have the experience 

 of other observers. Annual plants dependent upon the ferti- 

 lization and dispersion of seeds for their reproduction^ ought 

 naturally to have greater facility for promoting the fecundation of 

 the ovules than plants provided with other means of i^e prod notion. 

 Thus it is that M. Lecoq accounts for the great rarity of dioe- 

 cious annual plants. From this author we cite the following 

 facts, Unisexuality is more common in perennial than in annual 

 plants, and in both, monoecious plants are more common than 

 dioecious. Referring especially to Central France, he gives these 

 statistics, which will apply nearly as well to the rest of Europe. 

 Of 563 annual plants 16 are monoecious, or 1 in 35. Of 1,245 

 perennial and woody plants, 147 are unisexual, or 1 in 8*5 ; and 

 of the 147, 103 are monoecious, or 1 in 12 of all perennials, and 

 44 dioecious, or 1 in 28, and of these latter the majority are 

 trees and shrubs, often lofty, and provided with an abundance of 

 pollen. 



Another provision of Nature for ensuring the fertilization in 

 unisexual plants, especially in dioecious ones, is shown in the fact 

 that such plants have either small and imperfect floral envelopes, 

 or, it may be, none at all, and thus access of the pollen to the 

 stigma is facilitated. In hermaphrodite flowers the provisions 

 are equally marked to ensure the due contact of the pollen with 

 the stigma, but here it is by the presence of protecting envelopes, 

 by the situation of the stamens, etc. 



From these circumstances it becomes a question whether it 

 would not be possible to convert a dioecious plant into a monoe- 

 cious, or even into an hermaphrodite one, by checking the forma- 

 tion of shoots, by encouraging the formation of flowers at the 

 expense of leaves, or by other means. That this is not so wild a 

 notion as at first sight it may appear, is shown by the numerous 

 recorded instances of dioecious plants becoming occasionally 

 monoecious, or even perfecting hermaphrodite flowers. 



What are the circumstances which have tended to such re- 

 sults ? Again, is there any possibility of ensuring with certainty 

 the growth of either sex from seed ? 



