n LENTIBULARIACE^ 279 



terminal part grows into a compact bud, and thus 

 passes the winter. 



PiNGUlCTJLA (Butterwort). 



The corolla is spurred as in Utricularia, but with 

 a broad open mouth. There are three British species : 

 F. vulgaris, with violet - purple, P. alpina and P. 

 lusitanica, with yellow flowers. In P. alpina the spur 

 is very short, and nearly straight, while in P. lusitanica 

 it is longer and curved. The plant grows in damp 

 places. " It bears on an average eight, rather thick, 

 oblong, light green leaves, having scarcely any foot- 

 stalk. A full-sized leaf is about 1^ inch in length and 

 |- inch in breadth. The young central leaves are deeply 

 concave, and project upwards ; the older ones towards 

 the outside are flat or convex, and lie close to the 

 ground, forming a rosette from 3 to 4 inches in diameter. 

 The margins of the leaves are incurved (Figs. 179, 

 180). Their upper surfaces are thickly covered with 

 two sets of glandular hairs, differing in the size of 

 the glands and in the length of their pedicels (Fig. 181). 

 The larger glands have a circular outline as seen from 

 above, and are of moderate thickness ; they are divided 

 by radiating partitions into sixteen cells, containing 

 light-green homogeneous fluid." ^ The glands secrete 

 a colourless fluid which is so viscid that Darwin was 

 able to draw out a thread to a length of no less 

 than 18 inches. It has been calculated that an 

 ordinary rosette of leaves bears about 500,000 of such 

 glands. Any small insect alighting on the leaves is 

 thus caught : the edge curves over, which appears to 

 be an advantage in two ways, partly in preventing the 

 victim from being blown away, and partly by pushing 

 it slightly towards the centre of the leaf, where there 

 are more glands. Seeds, small fruits, pollen, etc., are 

 also caught. Thirty-two leaves examined by Darwin 

 had 142 insects adhering to them, or rather more than 

 four each. 



' Darwin, Insectivorous Plants. 



