69 



to attract insects. Id some flowers as in dandelion, all of 

 the corollas are strap-shaped. In boneset, the ray-fl )wers are 

 absent. 



This large order has some extreme varations, as in Am- 

 brosia which is anemophilous. In many the nectar is easily 

 reached by short tonorued insects, as in SoUdago Achillea. 

 In some thistles, as Cnicus lanceolatus, the nectar can only be 

 reached by long tongued insects. Where the individual flow 

 er sometimes lacks in attraction the ray flowers increase in 

 conspicuousness. 



Vernoniafasciculata Michx. grows in marshes. The tall stems 

 bear numerous heads of purple fl'owers. The long tubular 

 flowers are adapted to long tongued bees and flies, also Lepi- 

 doptera. The flowers are proterandrous, the pollen being 

 carried out by the brush hairs on the style. 



The Eupatorium ageratoides L. isa'so without ray flowers 

 but grows in woods. It flowers at the same time that Ver- 

 nonia does. The E. purpureum L. var. Maculatum grows 

 in woods and is a competitor with the above. The purple 

 color of the flower renders it more attractive. The E. pur- 

 pureum competes with E.perfoliatum, L. growing in similar 

 places, but is purple flowered. 



in yarrow or milfoil {^Achilha millefolium) the white heads 

 are attractive to insects. A single flower is small and incon- 

 spicuous, but many of these small flowers are crowded to- 

 gether in one head, and in addition the white ray-flowers 

 certainly render them conspicuous. The nectar is easily 

 reached by many insects. It is secreted by a small disc at 

 the base of the style. The flowers are strongly proterand- 

 rous. Each flower has flve stamens. The anthers are united, 

 and when the flower opens the two divisions of the style are 

 closely appressed in a cylinder made by the five anthers. 



