474 



BEES AND FLOWERS. 



the style (sf/) scarcely reaches beyond the middle of the tube of the 

 corolla and the stamen^ (a') are placed near the orifice; others (A) 

 where the position is reversed, the style {st) extending to the orifice 

 and the stamens forming a ring in the center of the tube. 



To this remarkable clilference is added another hardly less curious; 

 the pollen of the short-styled flowers is large grained (pg^) while the 

 pollen of the others comes in very small grains ipg). These plants 

 are therefore as ill adapted as possible to direct fertilization or cross 

 fertilization through the action of the wind. Some sort of insect 

 intervention becomes almost necessary. A\'lien a bee goes into one of 

 the short-styled flowers (B) he strikes the stamen with his head and 

 covers it with |)olleii dust. A\'hen he enters a flower of the other sort 



Fig. ;i.— Orchid flowers and llicir fertilization l>y bees. 



A. Flower of Orchis moria, with the sepals, two petals, and a bit of the right side of the spur re- 

 in< ived. This fl( )wer is visited by a bee which receives on its face the sticky pollen mass from i /' i . 

 B. This ]H)llen is carried to another flower which receives it on its sUgma (.s/ ), after which 

 another mass ( pn ) is carried away by the visitoi'. C. Same as A, viewed from front to show 

 entrance to spurs and the antler (ff). D. Isolated mass of pollen (po) fixed on the rostellnm. 

 E, F, G. Successive positions taken by ])ollcn on bee's head. H. Disruption of pollen. I. 

 Vanda pollen on head of honeybee. 



(A) he brushes off on its stigma the large grains of pollen he carries 

 and with his proboscis gathers the little grains which will fertilize 

 the short-styled flowers. Darwin has made a profound stiuly of these 

 heterostyle plants and has demonstrated that their fei'tilization is 

 almost ahvays by crossing effected by the visits of insects. 



Among the violets, the Aristolochiacea^ and many other Phanero- 

 gams, the arrangement of the parts of the flower renders even more 

 necessary tlie iiiter\ention of insects, but T pass them over in ord(M' to 

 reach the orchids, where in almost vvovy case this intei'venl ion is al>so- 

 liitely necessary. 



