Revolver Flowers. 119 



weight to produce the necessary motion of the cal- 

 ceolus, and that therefore would touch neither stigma 

 nor pollen, have no possible means of getting to the 

 nectar. 



In aU these cases it is by curvature of the 

 perianth, or of its appendages, that the narrowing of 

 the passage leading to the nectary is effected. There 

 are, however, many other cases where the same result 

 is obtained by special developments of the andrce- 

 cium ; and among them are some where the result- 

 ing forms are of extreme elegance. Such, for iu- 

 stance, are those where the . filaments, thickened, or 

 expanded into a petaloid condition, and adherent to 

 the inner surface of the perianth, send out processes 

 which jut into the central space of the tube, and parti- 

 tion it out into a number of precisely similar passages. 

 These passages, which are usually five or six ia num- 

 ber, stand in a circle round the central ovary; so 

 that a transverse section of the flower gives the im- 

 pression of a five-barrelled revolver. Such passages 

 are, as a rule, very narrow, and allow nothing thicker 

 than a proboscis to penetrate to the nectar, to which 

 they lead. But it is only insects that have this 

 proboscis that are welcome guests to these " revolver- 

 flowers ; " for they alone are of such suitable size and 

 weight as to repay their share in the feast by pro- 

 moting allogamy. Other insects, whose visits would 

 confer no such advantage, are shut out from the nectar 



