278 DICECIOUS AND CHAP. VII. 



CHAPTER VII. 

 POLYGAMOUS, DICECIOUS, AND GYKO-DICECIOUS PLANTS. 



The conversion in various ways of hermaphrodite into dioecious plants 

 Heterostyled plants rendered dioecious Rubiacese Verbenaceae 

 Polygamous and sub-dioecious plants Euonymus Fragaria 

 The two sub-forms of both sexes of Khamnus and Epigsea Ilex 

 Gyno-dicecious plants Thymus, difference in fertility of the her- 

 maphrodite and female individuals Satureia Manner in which 

 the two forms probably originated Scabiosa and other gyno-dice- 

 cious plants Difference in the size of the corolla in the forms of 

 polygamous, dioecious, and gyno-dicecious plants. 



THERE are several groups of plants in which all the 

 species are dioecious, and these exhibit no rudiments 

 in the one sex of the organs proper to the other. 

 About the origin of such plants nothing is known. It 

 is possible that they may be descended from ancient 

 lowly organized forms, which had from the first their 

 sexes separated; so that they have never existed as 

 hermaphrodites. There are, however, many other 

 groups of species and single ones, which from being 

 allied on all sides to hermaphrodites, and from exhib- 

 iting in the female flowers plain rudiments of male 

 organs, and conversely in the male flowers rudiments 

 of female organs, we may feel sure are descended from 

 plants which formerly had the two sexes combined in 

 the same flower. It is a curious and obscure problem 

 how and why such hermaphrodites have been rendered 

 bisexual. 



If in some individuals of a species the stamens 

 alone were to abort, females and "hermaphrodites would 



