474 



BEES AND FLOWEES. 



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

 coi-olhi 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 difference is added another hardly less curious; 

 the pollen of the short-styled flowers is large grained {p(/') while the 

 pollen of the others conies in very small grains (pf/). 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. When a bee goes into one of 

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

 covers it with pollen (hist. AMieii he enters a flower of the other sort 



(I rs .-P^ 



Fi(i. ;i.— Orchid flowers and their fertilization hy bees. 



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

 moved . This ill )wer is visited l)y a bee which receives on its face the sticky pollen mass from ( r ) . 

 B. This pollen is carried to another flower which recidves it on its stigma {st}, after which 

 another mass ip<>) is carried away by the visitor. C Same as A, viewed from front to show 

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

 E, P, G. Successive positions taken by pollen 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. Dai'win has made a profound study of these 

 heterostyle ])lants and has demonstrated that their fertilization is 

 almost always by crossing effected by tlie visits of insects. 



Among the violets, the Aristolochiac(>a> and many other Phanero- 

 gams, the arrangement of the i)arts of the flower renders even more 

 necessary the intervention of insects, but I pass them over in order to 

 reach the orchids, where in ahuost every case this intervention is al)So- 

 lutely necessary. 



