280 BRITISH FLOWERING PLANTS chap. 



P. vulgaris. — As regards arrangement the flowers of 

 Pinguicula differ from those of Utricularia principally 

 in being adapted to small bees, in being open, and in 

 not having a sensitive stigma. The latter is in the present 

 genus pushed back by the retreating head of the bee. 



Fig. 180. 



Figs. 179, 180. — Transverse section through the leaf of a Butterwort {Pinguicula 

 alpina). Fig. 179, nat. size. Fig. 180, x 50. 



P. alpina. — This species has protogynous flowers, and 

 is mainly visited by flies, which creep into the flower 

 until their head reaches the base of the spur. In almost 

 all cases the presence of a spur or a tube in flowers 



indicates that of honey. P. 

 alpina, however, is said to 

 be honeyless, but the inner 

 side of the spur is clothed with 

 glandular juicy hairs the con- 

 tents of which are very attractive 

 T^ 1 CI T.- ^ ^v J • ^ to insects. As the flower is pro- 



FiG. 181, — Piece of the epidermis of i it ■! 



a leaf of Butterwort, showing togynOUS, the tilCS nCCeSSarUy 



and sTaiked^'^'xfso!*"'^' ''''"^ ^^^^^ cross-fertiHsatiou, carry- 

 ing the pollen from older flowers 

 to those more recently opened. The bristles give 

 an easy entrance, but are supposed to make the with- 

 drawal of the head more gradual, and in other cases 

 prevent it altogether, the fly being thus treacherously 

 captured. Thus P. alpina is doubly an insect-capturing 

 plant. 



