396 THE BIOLOGY OF FLOWERING PLANTS 



Cleistogamous flowers have been regarded as specialised 

 structures which insure the plant against the chance failure 

 of the open flowers to set seed. Goebel (1904 and Org.) 

 has shown, however, that essentially they are flowers in 

 which development is inhibited at an early stage. In the 



Fig. 61. — Cleistogamous flowers: i, Cardamine chenopodiifolia, at F 

 the cleistogamous flowers penetrating the soil ; 2 and 3, Viola syhatica, 

 cross-sections through flowers, sepals shaded, petals black; 2 is an in- 

 termediate between the open and the cleistogamous flower, 3. (After 

 Goebel.) 



violet the sepals are normal, though small, the petals are 

 represented by five whitish scales, and the spur is not 

 developed. Five stamens are present, but only two sporangia 

 are developed in each ; the staminal spurs are wanting. 

 The stigma remains hidden among the stamens. The 

 endothecium is reduced and does not function, the pollen 



