294 DICECIOUS AND CnAP. VU 



known to be dioecious. My son William found the 

 two sexes growing in about equal numbers in the Isle 

 of Wight, and sent me specimens, together with obser- 

 vations on them. Each sex consists of two sub-forms. 

 The two forms of the male differ in their pistils: 

 in some plants it is quite small, without any distinct 

 stigma ; in others the pistil is much more developed, 

 with the papillae on the stigmatic surfaces moderately 

 large. The ovules in both kinds of males are in an 

 aborted condition. On my mentioning this case to Pro- 

 fessor Caspary, he examined several male plants in 

 the botanic gardens at Konigsberg, where there were 

 no females, and sent me the accompanying drawings. 



Fig. 13. 



Long-styled male. Short-styled male. 



Rhamnus CATHARTions. (From Caspary.) 



In the English plants the petals are not so greatly 

 reduced as represented in this drawing. My son ob- 

 served that those males which had their pistils mode- 

 rately well developed bore slighly larger flowers, and, 

 what is very remarkable, their pollen-grains exceeded 

 by a little in diameter those of the males with greatly 

 reduced pistils. This fact is opposed to the belief that 

 the present species was once heterostyled ; for in this 

 case it might have been expected that the shorter- 

 styled plants would have had larger pollen-grains. 



In the female plants the stamens are in an ex- 

 tremely rudimentary condition, much more so than 



