286 DICECIOUS AND Chap. VII. 



ovarium, surmounted by a mere yestige 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 Rubiaceous plant becoming dioecious. 

 Moreover, in an allied plant, Galium cmciatum, 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 loculus 

 contains several perfect ovules ; so that the species 

 appears to be strictly dioecious. 



Most of the species of the South American genus 

 j3Egiphila, a member of the Verbenacese, apparently 

 are heterostyled; and both Fritz Miiller and myself 

 thought that this was the case with ^. dbdurata, 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 thiiik, conclude that a short-styled progenitor, 



