354 FIELD AND WOODLAND PLANTS 



are thi'cc or four inches high, each bearing a single violet flower. 

 In this species the throat of the corolla is bell-shaped, and the spnr 

 is as long as the rest of the corolla. 



A second species — the Alpine Butterwort (P. alpina) — with 

 smaller, pale yellow flowers appearing in June and July, is found 

 only in Scotland ; while a third, known as the Pale Butterwort 

 (P. lusitanica), also with pale 3'ellow flowers, and a curved spur, 

 occurs in South-West England as well as in the boggy districts of 

 Ireland and the West of Scotland, flowering from June to October. 



The carnivorous habits of all species are the same. The horizon- 

 tal leaves lie flat on the wet soil, with their margins turned upward 

 forming a kind of shallow trough ; and the upper surface of each is 

 dotted with many hundreds of minute glands which secrete a 

 colourless, sticky fluid, thus giving to the leaf its glistening and 

 clammy appearance. 



If any mineral or other non-nutritious substance be placed on a 

 leaf, the contact stimulates the little glands, causing them to 

 discharge a larger quantity of fluid, but no change seems to take 

 place in the character or composition of the secretion. But if any 

 nitrogenous organic suljstance, such as an insect or a small piece 

 of meat, be brought in contact with the glands, not only \Aill the 

 secretion increase in quantity, but it will also assume an acid 

 character, and contain a ferment which is capable of digesting the 

 nitrogenous material. In fact, the secretion produced under these 

 circumstances possesses the same properties as the gastric fluid of 

 the stomachs of animals. 



The animal food of the Butterworts consists of small insects and 

 other little creatures. If an insect alights on the leaf, it is caught 

 by the sticky secretion of the glands, and every efi^ort to escape 

 causes it to become more and more besmeared v.ith the mucilage, 

 till, at last, it is no longer able to move ; and its death is probably 

 hastened by the stoppage of its spiracles or breathing-holes. 



If the insect is a small one, and it settles near the edge of the 

 leaf, the curved margin slowly bends over it until it is more or less 

 enclosed, and the larger number of glands thus brought in contact 

 with its body pour out their digestive secretion, which slowly 

 dissolves the nourishing portions, leaving nothing but the legs, 

 wings, and other indigestible parts. A larger insect, alighting 

 similarly near the edge of the leaf, could hardly be enclosed by the 

 bending of the margin near it ; but it is pushed towards the middle 

 as the edge curls over, and then the opposite side also bends over 



