276 BRITISH FLOWERING PLANTS chap. 



three species : U. intermedia is distinguished by the 

 bladders being on separate branches ; in U. vulgaris 

 the spur is conical ; in U. minor it is very short. 

 They are said to be fly flowers, the entrance of the 

 corolla being too narrow for bees. It is seldom that 

 flies show sufficient intelligence to avail themselves 

 of a flower so complicated. The remarkable bladders, 

 from which the genus derives its name, have been speci- 

 ally studied by Cohn ^ and Darwin.^ Darwin worked 

 mainly with U. neglecta. The bladders, he says, " are 

 supported on short foot-stalks. When fully grown they 

 are nearly one-tenth of an inch (2 '5 4 mm.) in length. 



Fig. 176. — Utricularia vulgaris. Bladder much enlarged, c, collar indistluctly seen 

 through the walls ; e, entrance ; d^ a small Crustacean (Chydorus) which has 

 been captured. 



They are translucent, of a green colour, and the walls 

 are formed of two layers of cells. The exterior cells are 

 polygonal and rather large ; but at many of the points 

 where the angles meet, there are smaller rounded cells." 

 The interior is lined with a serried mass of absorbent 

 processes, in groups of four, two long and two short. 

 The general form is shown in Fig. 176. The lower side 

 is nearly straight, the upper much arched, and terminates 

 in some long processes, two of which are larger than 

 the rest and branched, giving the whole organ a curious 

 resemblance to a Daphnia. At the angle is an entrance 



^ Cohn, " Ueber d. function der Blasen von Aldrovanda u. Utriculaiia," Beilr. 

 Biol. Pflansen, i. Heft 3 (1875). 

 ^ Darwin, Insecliiiorous Plants. 



