Chap. VII. POLYGAMOUS PLANTS. 293 



■ 



climate on the reproductive organs. In the best ac- 

 count which I have seen,* it is stated that many of the 

 varieties in the United States consist of three forms, 

 namely, females, which produce a heavy crop of fruit,- 

 of hermaphrodites, which "seldom produce other than 

 a very scanty crop of inferior and imperfect berries/' 

 — and of males, which produce none. The most skilful 

 cultivators plant " seven rows of female plants, then 

 one tow of hermaphrodites, and so on throughout the 

 field." The males bear large, the hermaphrodites 

 mid-sized, and the females small flowers. The latter 

 plants produce few runners, whilst the two other forms 

 produce many; consequently, as has been observed 

 both in England and in the United States, the polleni- 

 ferous forms increase rapidly and tend to supplant the 

 females. We mav therefore infer that much more vital 

 force is expended in the production of ovules and fruit 

 than in the production of pollen. Another species, the 

 Hautbois strawberry (F. elatior), is more strictly dioe- 

 cious; but Lindley made by selection an hermaphrodite 

 stock, f 



Rhamnus catliarticus (Khamneae). — This plant is 

 well 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 stig- 

 ma; in others the pistil is much more developed, with 

 the papilla* on the stigmatic surfaces moderately large. 

 The ovules in both kinds of males are in an aborted con- 

 dition. On my mentioning this case to Professor Cas- 



* Mr. Leonard Wray in ' Gard. formation on this subject, see 

 (iron/ 1861, p. 716. 'Variation under Domestication/ 



iron,' 1861, p. 716. variation umin v«ww»wi 



t For references and further in- chap. x. 2nd edit. vol. i. p. 375. . 



