THE ANGIOSPERMAE 



1355 



development, the corolla, which is normally late in appearing, being absent. 

 ChasmogamoLis flowers are produced later. 



Fig. 1262. — Cardamiue chenopodiifoUa. A, Plant with under- 

 ground cleistogamous flowers and chasmogamous flowers 

 developing aerially. B, Siliqua from chasmogamous flower. 

 C, Siliqua from cleistogamous flower. {After Velenovsky.) 



By far the greater number of cleistogamic plants may be called facultative. 

 They are of mixed type and bear both kinds of flowers, either as a regular 

 feature or occasionally, when conditions determine it. Among the latter are 

 the seasonal cleistogams, such as Lamium amplexicaule whose cleistogenes 

 appear in the earliest spring, and Oxalis acetosella and Viola odorata, growl- 

 ing in shady places, which open their chasmogamous flowers in the spring, 

 but later, when overgrown by other vegetation, bear only cleistogenes. 



Exclusively cleistogamous species are much rarer. Two British plants 

 in this category are the small and uncommon Subnlaria aquatica and Poly- 

 carpon tetraphyllum. Leersia oryzoides has also been named above and it may 

 be pointed out that in this and other Grasses, no question of any lack of 



