LENTIBULARIACE^ 



277 



closed by a flap (Fig. 177, 178, c), whicli plays freely on 

 a rim or collar. This flap is easily pressed inwards, but 

 then springs back into place. Minute fresh- water Crus- 

 tacea and insects seem to have a singular fascination for 

 entering, and once 

 in, as they cannot 

 open the flap from 

 inside, they are 

 doomed. Darwin 

 found in one 

 bladder as many 

 as ten minute 

 Crustacea. The 

 walls of the en- 

 trance (Fig. 177, 

 a) are slightly 

 contracted in 

 the centre like 

 (though not so 

 much as) an hour- 

 glass ; and the 

 flap (6), shown by 

 the dotted line, 

 being nearly semi- 

 circular, can open 

 inwards, but not 

 outwards. 



U. vulgaris. — 

 The arrangement 

 of the flower in 

 some respects re- 

 sembles that of 

 Antirrhinum (Snapdragon). The two lips of the 

 corolla completely close the flower. The upper lip is 

 simple : the lower consists of three parts (Fig. 175, 1) 

 — (1) the spur which contains the honey; (2) the 

 arched prominence which abuts against the upper lip 

 and closes the flower; and (3) the lateral projecting 

 lobes. These serve as an alighting stage for the 



Fio. 177. — Utricularia vulgaris. Opening of bladder, 

 seen in front ; much enlarged, a, "wall of opening ; 

 6, outline of the flap ; o, opening. 



