HO HETEROSTYLED DIMORPHIC PLANTS. CHAP. III. 



when applied to the stigmas of the short-styled flowers. 

 With several species of Primula the short-styled 

 flowers are much more sterile than the long-styled, 

 when both are illegitimately fertilised; and it is a 

 tempting view, as formerly remarked, that this greater 

 sterility of the short-styled flowers is a special adapta- 

 tion to check self-fertilisation, as their stigmas are 

 eminently liable to receive their own pollen. This view 

 is even still more tempting in the case of the long- 

 styled form of Linum grandiflorum. On the other hand, 

 with Pulmonaria angustifolia, it is evident, from the 

 corolla projecting obliquely upwards, that pollen is 

 much more likely to fall on, or to be carried by insects 

 down to, the stigma of the short-styled than of the 

 long-styled flowers ; yet the short-styled, instead of being 

 more sterile, as a protection against self-fertilisation, 

 are far more fertile than the long-styled, when both 

 are illegitimately fertilised. 



Pulmonaria azurea, according to Hildebrand, is not 

 heterostyled.* 



From an examination of dried flowers of Amsinclcia 

 spectabilis, sent me by Professor Asa Gray, I formerly 

 thought that this plant, a member of the Boraginese, was 

 heterostyled. The pistil varies to an extraordinary degree in 

 length, being in some specimens twice as long as in others, 

 and the point of insertion of the stamens likewise varies. 

 But on raising many plants from seed, I soon became con- 

 vinced that the whole case was one of mere variability. The 

 first-formed flowers are apt to have stamens somewhat ar- 

 rested in development with very little pollen in their an- 

 thers; and in such flowers the stigma projects above the 

 anthers, whilst generally it stands below and sometimes 

 on a level with them. I could detect no difference in the 

 size of the pollen-grain or in the structure of the stigma 

 in the plants which differed most in the above respects ; and 



* 'Die Gesclilcchter-Vertheilung bei den Pflanzen,' 1867, p. 37. 



