286 DKBOIOUS AND Chap. VU. 



ovarium, suxmounted by a mere vestige of a stigma 

 without any style ; whilst the female flowers possess 

 a large ovarium, the anthers being rudimentary and 

 apparently quite destitute of pollen. Considering 

 how many Rubiaceous genera are heterostyled, it is a 

 reasonable suspicion that this Asperula is descended 

 from a heterostyled progenitor ; but we should be 

 cautious on this head, for there is no improbability in 

 a homostyled Eubiaceous plant becoming dioecious. 

 Moreover, in an allied plant, Galium crudatvm, the 

 female organs have been suppressed in most of the 

 lower flowers, whilst the upper ones remain hermaph- 

 rodite ; and here we have a modification of the sexual 

 organs without any connection with heterostylism. 



Mr. Thwaites informs me that in Ceylon various 

 Rubiaceous plants are heterostyled ; but in the case 

 of Discospermum one of the two forms is always 

 barren, the ovary containing about two aborted ovules 

 in each loculus ; whilst in the other form each loctilus 

 contains several perfect ovules ; so that the species 

 appears to be strictly dioecious. 



Most of the species of the South American genus 

 JEgiphila, a member of the Verbenaceas, apparently 

 are heterostyled; and both Fritz Miiller and myself 

 thought that this was the case with Mi. obdurata, so 

 closely did its flowers resemble those of the heterostyled 

 species. But on examining the flowers, the anthers of 

 the long-styled form were found to be entirely desti- 

 tute of pollen and less than half the size of those in 

 the other form, the pistil being perfectly developed. 

 On the other hand, in the short-styled form the stig- 

 mas are reduced to half their proper length, having 

 also an abnormal appearance ; whilst the stamens are 

 perfect. This plant therefore is dioecious ; and we 

 may, I think, conclude that a shortrstyled progenitor, 



