296 DIOECIOUS AND CHAP. VIL 



son compared the pollen-grains from the two forms, 

 and those from the long-styled flowers were to those 

 from the short-styled, on an average from ten measure- 

 ments, as 10 to 9 in diameter ; so that the two her- 

 maphrodite forms of this species resemble in this 

 respect the two male forms of R. catharticus. The 

 long-styled form is not so common as the short-styled. 

 The latter is said by Asa Gray to be the more fruitful 

 of the two, as might have been expected from its 

 appearing to produce less pollen, and from the grains 

 being of smaller size ; it is therefore the more highly 

 feminine of the two. The long-styled form produces 

 a greater number of flowers, which are clustered to- 

 gether instead of being sub-solitary ; they yield some 

 fruit, but as just stated are less fruitful than the other 

 form, so that this form appears to be the more mas- 

 culine of the two. On the supposition that we have 

 here an hermaphrodite plant becoming dioecious, there 

 are two points deserving notice; firstly, the greater 

 length of the pistil in the incipient male form ; and 

 we have met with a nearly similar case in the male 

 and hermaphrodite forms of Euonymus compared with 

 the females. Secondly, the larger size of the pollen- 

 grains in the more masculine flowers, which perhaps may 

 be attributed to their having retained their normal size ; 

 whilst those in the incipient female flowers have been 

 reduced. The long-styled form of R. lanceolatus seems 

 to correspond with the males of R. catharticus which 

 have a longer pistil and larger pollen-grains. Light 

 will perhaps be thrown on the nature of the forms 

 in this genus, as soon as the power of both kinds of 

 pollen on both stigmas is ascertained. Several other 

 species of Rhamnus are said to be dioecious* or sub- 



Lecoq, 'Geogr. Bot.' torn. v. 185G, pp. 420-26. 



