336 



CHAPTERS ON EVOLUTION. 



condition, each stamen is seen to consist of a stalk (the filament) 

 (/), to which another and movable stalk (the connective) (;;/), bearing 

 an anther-cell at each end, is attached. Only one of these anther- 

 cells (a 1 ) is fully developed in each stamen. The connective (///), 



like a swing-bar, can be pushed back- 

 wards on its axis so as to bring the 

 fully- developed or upper anther-cell (a 1 ) 

 to a horizontal position (Fig. 231, C). 

 Such a result is actually brought about 

 by the bee. Thrusting its head into 

 the flower in the search for nectar, the 

 insect pushes before it the lower end 

 of the. swing-bar, and thus brings the 

 upper end of the bar with its ripe 

 anther (a 1 ) in contact with its back 

 (Fig. 232, A). This latter region is 

 thus dusted with pollen, and when the 

 insect flies to another Salvia flower in 

 which the pistil is ripe, the stigma 

 (Fig. 232, B j/), as we have seen, will in 

 due course receive the pollen through 

 contact with the back of the bee. 



A single paragraph only is permissible regarding the curious 

 details connected with the fertilisation of the Orchids, which possess 



FIG. 238. ORCHID FLOWER. 



FIG. 239. POLLEN MASSES OF ORCHID. 



FIG. 240. SECTION OF ORCHID FLOWER. 



flowers (Fig. 238) of markedly irregular shape. The lip (//) in such 

 a flower as Orchis mascula, a common British species, is very broad ; 

 whilst the nectary to which bees desire admittance is extremely long 

 (Fig. 240,;?). The pollen forms two club-shaped masses (Figs. 239, 



