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154 THE STORY OF THE PLANTS. 



no doubti for petals, are very different indeed 

 from these central blossoms. They have an 

 extremely cm'ious long, strap-shaped corolla 

 (Fig. 35), open down the side, but tubular at its 

 base, as if it had been split through the greater 

 part of its length by a sharp penknife. Instead 

 of being yellow, too, these outer florets are 

 white, slightly tinged with pink, and they form 

 the largest and most attractive part of the whole 

 flower-head. Furthermore, they are female 

 only ; they have a style and ovary, but no 

 stamens. Clearly, we have here a flower-head 

 with numerous unlike flowers, which at once 

 suggests the idea of a division of labour between 

 the component members. How this division 

 works we shall see in the sequel. 



The best way to see it is to follow up in detail 

 the evolution of the daisy and the other com- 

 posites from an earlier ancestor. We saw 

 already how the petals combined in the harebell 

 and many other flowers so as to form a tubular 

 corolla. A purple flower of some such type 

 seems to have been the starting-point for the 

 development of the great composite family. The 

 individual blossoms in the common ancestral 

 form seem to have been small and numerous ; 

 and, as often happens with small flowers, they 

 found that by grouping themselves together in 

 a flat head they succeeded much better in 

 attracting the attention of the fertilising insects. 

 Many otlier tubular flowers that are not com- 

 posites have independently hit upon the same 

 device ; such are the scabious, the devil' s-bit, 

 the sheep's-bit, and the rampion. But these 



