FLORAL MECHANISMS 



121 



flowers, with the exception of the orchids, is that 

 of the common milkweed. It seems strange that 

 this rank herb should resort to such elaborate means 

 to procure cross-fertilisation, and remarkable also 

 that no similar mechanism has been evolved by other 

 plants. The milkweed shows inventive genius. Its 

 flowers are very small and clus- 

 tered in a loose bunch, of delicate 

 lilac or lavender-brown colour, 

 and emit a heavy, cloying fra- 

 grance. We see them in the op- 

 posite drawing as they droop in 

 a loose bunch of some twenty 

 florets. Around and upon them 

 various insect visitors are always 

 to be found, and we usually see 

 the flowers tossing and swaying 

 under their eager thrusts. We 

 see the insects cling and swing by their hind legs 

 clasped against the neck of the flower, as in the 

 sketch, and sometimes a leg caught as in a trap, 

 while the whole cluster quivers as the insect fran- 

 tically strives for freedom. 



Let us pluck a single floret, like the topmost 

 sketch, and examine it. 



We see the calyx bent back, and the narrow neck 

 to which the insects cling, and five nectar-horns, 



BEE ON MILK- 

 WEED 



