OF DENISON UNIVERSITY. 



13 



now opened, and the stigma laid bare to catch the pollen from the bee's 

 back, where it has been deposited by another flower, as previously de- 

 scribed. 



The general arrangement for cross-fertilization in the florets of the 

 Compositae is the same as that just described for the LobeliacecC. But 

 the vast number, the wide distribution, and the varied habits of the 

 genera and species under the Compositae cause many special variations. 

 These variations are shown especially by the arrangements of the hairs 

 and the stigmatic papillae. In some genera, just as in the Lobelia, 

 these hairs sweep the pollen before them, forming a simple ring around 

 the style at the base of the stigmas or aggregated in a tuft at the ex- 

 tremity of the stigmas. In other genera they spread over more or 

 less of the surface of the style and the pollen is entangled among them. 

 The mechanism for pushing out the pollen is farther perfected in some 

 Compositae by the contraction of the filaments of the stamens on being 

 touched by the proboscis of the insect. 



