DEGENERACY OF FLOWERS. 263 



and abundantly in all parts England. Viola nana bears 

 normal flowers in its native home in India, but only cleisto- 

 gamous ones in England. Viola palustris bears only the 

 larger flowers near Pai'is, which are perfectly fertile, but 

 when it grows on mountains it bears cleistogamous flowers. 

 Similarly Impatiens fulva bears both kinds of flowers m Eng- 

 land, but the larger are usually barren. After midsummer, 

 in its native home in the United States, these flowers will 

 produce capsules. Salvia clandestina, when transplanted 

 from Africa to Halle, bore only cleistogamous flowers for 

 five years, according to Ascherson, who considered the plant 

 to afford an example of continuous self-fei-tilisation. He, 

 however, afterwards observed ordinary open flowers. It is 

 a species particularly common on the Continent. 



Again, plants vary according to the season. Thus Mr. 

 Darwin found that Vandellia nummularifolia bore no perfect 

 flowers in one season ; so, too. Ononis columnce bore none in 

 1867, yet it had both kinds in 1868. 



The time of the year also influences the production of 

 cleistogamous flowers. Thus Ononis rainuHssima, parviflora, 

 and 0. columnce, according to Mr. Bentham, produce them 

 early in the spring. Godetia Gavanillesii and Lamium am- 

 plexicaule do the same ; while some bear a fresh crop in the 

 autumn, as 0. columnce. 



Two cases are mentioned by Mr. Darwin in which the 

 period is the reverse of the above. 



Viola Boxburgliiana bore abundance of cleistogamous, but 

 no perfect flowers, in Mr. Darwin's hothouse ; and it bears 

 the perfect flowers in India " only during the cold season, 

 and these are quite fertile. During the hot, and more 

 especially during the rainy season, it bears an abundance 

 of cleistogamous flowers."* 



* Forms, etc., p. 320. 



