18 INTRODUCTORY 



in the case of sea foam, our eyes experience the 

 sensation which we call whiteness. The hair cells of 

 the Edelweiss produce a similar effect. 



The Higher Plants have, as a rule, green leaves and 

 often green stems, and this is true also of the Edel- 

 weiss, but the green colour is here masked by the 

 coat of hairs. 



The leaves of the Edelweiss, like those of many 

 other Alpines, are arranged in a small rosette just 

 above the soil. A single stalk springs from the 

 leaves bearing what, at first sight, appears to be a 

 solitary flower, but which in reality is a very com- 

 plicated structure consisting of several flower-heads, 

 each with a large number of individual flowers. It 

 is one of the peculiarities of the order Compositae 

 to which the Edelweiss belongs, that the flowers 

 should be all massed together into one or more heads. 

 The single heads of a Daisy or a Sunflower, for 

 instance, are not flowers, but collections of a large 

 number of flowers, seated on a broad receptacle. If 

 we cut one of these heads through with a pocket- 

 knife lengthwise, we can see the receptacle, and also 

 separate the individual flowers from one another.^ 



At the same time, the head performs all the 

 functions of a single flower, and is in itself an adapta- 

 tion designed for that very purpose. In the Edelweiss, 

 however, the heads are very small and yellowish in 

 colour, and, further, they are grouped together into 



' For a full account of the head of a Composite, see Appendix II., 

 p. 330. 



