96 



BRITISH FLOWERING PLANTS 



or trees. Viola is the only European genus, and extends 

 over most of the world. 



Viola (Violet) 



The flowers are yellow, white, blue, or violet, which 

 indeed has derived its name from the flower. The lower 

 petal is spurred, giving its peculiar form to the flower. 

 The anthers of the two lower stamens, as Sprengel 

 first pointed out, send each (Fig. 58) a projection into 

 the spur of the petal ; all five have a membranous 



Fig. 58. — Viola canina. 1, Section of a flower. 2, Stamen, a, anther ; c, mem- 

 branous expansion of connective ; /, iilameut ; h, hairs on petal to which pollen 

 grains have become attached ; n, nectary ; o, ovary ; p, petal ; po, pollen ; 

 5, sepal ; st, stigma. 



appendage, which together form a cup into which the 

 pollen is shed. The pistil projects upwards and closes 

 the mouth of the flower. The stigma is shaped more 

 or less like a bird's head. Insects only insert their 

 proboscis once in each flower. They naturally touch 

 the stigma flrst, then dust themselves with pollen 

 and transfer it to the next flower visited. The Violets 

 are as a rule bee -flowers, but some Alpine species 

 {V. calcarata, cornuta, etc.) have the spur elon- 

 gated and especially adapted for butterflies, while in 



