294 BRITISH FLOWERING PLANTS cii.u-. 



the head of a bee, the honey is accessible to insects with 

 a proboscis 8 mm. in length. As in other cases, the 

 pollen of the short-styled is larger than that of the long- 

 styled form.'' From the size of the flowers, the bright- 

 ness of the colours, the early season at which they open, 

 and the abundance of honey, they are richly visited by 

 insects, especially by bees and butterflies. Hildebrand 

 has shown ^ that the long-styled flowers are utterly 

 sterile to their own poUen, and even to pollen from 

 other plants of the same form. The short-styled flowers, 

 on the contrary, under such circumstances produce some 

 seed, though only about half as much as they do if 

 properly fertilised. The plant is covered with spread- 

 ing hairs. 



Mertensia 



This genus is glabrous, which is unusual in the 

 present family, but frequent among maritime plants. 



M. maritima. — A Northern and Arctic plant found 

 on our sea-shores in Wales, North England, and Scot- 

 land. 



LlTHOSPERMUM 



Nectar secreted by the base of the ovary, and concealed 

 at the base of the corolla-tube. Generally humble bee 

 flowers. We have three species : two have white or pale 

 yellow flowers ; one, L. arvense, is annual, with wrinkled 

 nuts ; the other, L. officinale, perennial, with smooth 

 nuts ; the third, L. purpureo-cceruleum, has bright blue 

 flowers. The name is derived from the extreme hard- 

 ness of the nuts (Xi'^o?, stone, and a-Trepfia, seed). 



L. arvense. — Flowers small and white, or on the 

 Continent sometimes blue. The nectar is protected by 

 hairs in the upper part of the corolla-tube. The anthers 

 open inwards and even before the flower, though the 

 flowers examined by Kerner were slightly protogynous. 

 The pistil ends in two short lobes, beneath which is a 

 ring of papillae, which are at the level of the anthers, 



1 See p. 288. ^ ^gt_ Zeit. xxiii. (1865). 



