THALAMIFLOR^ 103 



which recognises that species are even now, in 

 spite of Darwin's opinion, in the making.^ M. Jordan 

 recognised seventy forms of this species, and when 

 he cultivated them he found the characters constant. 



The Whitlow Grass is a good example of a plant 

 which has the rosette habit, with radical leaves, and 

 the aerial stem leafless, in the form of a scape, 

 specialised for bearing iiowers only. The rosette 

 habit is an adaptation to dry soil conditions. 



There is a reduction of the area of the surface, and 

 the radical leaves having the under-surface close to 

 the ground, the stomata or pores, by which the plant 

 transpires or gives off water vapour, derived from 

 the water absorbed by the root from the soil, are not 

 exposed to drought or to an excess of moisture. 

 Frequently the margins are rolled inwards in such 

 leaves, and there are hairs on the upper surface to 

 protect the leaves from too intense heat or light. 

 Such plants are also better rooted in the soil, and are 

 frequently annuals, as in this case. 



The radical leaves are ovate, lance-shaped, narrowed 

 below, toothed or entire, hairy, the hairs branched. 

 They are about an inch long, and more or less 

 horizontal. 



The flowers are white, borne on a leafless, smooth, 

 or rarely hairy scape, which is wavy. The calyx is 

 equal at the base. The petals are deeply notched. 

 The stigma is sessile in fruit. The stamens are not 



* 7.^. that species are being formed by a quick, not a slow process, 

 as Darwin held. 



