142 THE STORY OF THE PLANTS. 



here a flower-head with numerous unhke 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 blos- 

 soms 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 fer- 

 tilising insects. Many other tubular flowers that 

 are not composites have independently hit upon 

 the same device; such are the scabious, the 

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

 these flowers differ from the true composites in 

 two or three particulars. In the first place, each 

 tiny flower has a distinct green calyx, of five se- 

 pals ; while the composites have none, or at least 

 a degraded one. In the second place, the stamens 

 are free, while in the composites they have united 

 in a ring or cylinder. In the third place, the 

 ovary is divided into from two to five cells, a rem- 

 iniscence of the original five distinct carpels; 

 whereas in the composites the ovary is always 

 single and one-seeded. In all^ these respects, 

 therefore, the composites are later and more ad- 

 vanced types than, say, the sheep's-bit, which is a 

 flower-head composed of very tiny harebells. 



The composites, then, started with florets which 



