SPRINKLING APPARATUS. 



273 



pollen -dust on to the insect's back. In order that this complicated machinery- 

 may do its work successfully, the insect must insert its proboscis at a certain 

 definite spot through a little groove in the under lip, and for this reason all other 

 spots where entrance into the flower might be attempted are barricaded. The 

 margin of the upper lip, for instance, is thickly furnished with short-pointed 

 prickles which the insects take care not to touch (c/. figs. 276 1- ^- ^). 



The chief points of difference between the kinds of sprinkling apparatus 

 hitherto described and that which occurs in Acanthus flowers {Acanthus longi- 

 folius, A. mollis, A. spinosus; see figs. 277 1' 2, s) ^re that in the latter the anthers 



Fig. 277.— Sprinkling apparatus. 



1 Flower of Acanthus longifoUus with some of the petals cut away. 2 stamens of Acmithus illustrating the sugar-tongs 

 principle ; the anthers parted so as to let fall the pollen, 8 Single anther of Acanthus showing fringe. * Longitudinal 

 section through the flower of Rhinanthits angiistifolitis. ^ Stamen from the same, s xhe four stamens of Rbi-nanthus 

 seen from the entrance to flower ; the anthers in contact at the top, parted below ; the pollen falling out. 1 Flower of 

 Pyrola secunda with some of the petals and stamens cut away. « The same ; the anther is capsizing owing to the dis- 

 placement of the petal which has hitherto kept it in position, and pollen is being sifted through the pores. The arrow 

 in flgs. 1, ■* and 8 indicates the direction in which an insect enters the flower. 1, 2 natural size : the rest x 2 to 5. 



are unilocular instead of bilocular, and that the loculus resembles a long narrow 

 niche rather than the valve of a mussel-shell. Each niche is edged with close short 

 down, a provision which conduces materially to effective closure when the two 

 anthers are in contact. The filaments look as if they were made of ivory; they 

 are unusually strong, and are not so easily pushed asunder. Sturdy humble-bees 

 of large size alone are able to displace these filaments, and the result of their doing 

 so is to part the anthers and cause a shower of floury pollen to descend upon their 

 bodies. 



A form of sprinkling apparatus very diflferent from the sugar-tongs variety, 

 with its spoon-shaped anther lobes, is exhibited where the anthers act like pepper- 

 castors. Contrivances of this type occur chiefly in bell-shaped blossoms which are 

 either pendent or nodding. The anthers are furnished at or near their free 

 extremity with two little pores, and are so placed inside the bells as to have the 

 holes facing downwards at the moment when the pollen is to be scattered. The 



Vol. II. 



68 



