THE BUTTERWORTS 



213 



of these glands on a square centimetre of the leaf, 

 and consequently a plant with a rosette of six to nine 

 leaves is estimated to possess about half a million. 



In the photograph on Plate XLI., Fig. 2, two rosettes 

 of Pinguicula leaves are seen, thriving on a cushion of 

 damp moss, which is itself attached to the root of a 

 Spruce Fir. It will be noticed that numerous remains 

 of dead insects, chiefly flies, occur on the leaves of the 



Fio. XIX.'— The Common Butterwort {Pinguicula vulgaris, Linn.). 



1. Transverse section of a leaf, showing the glands on the upper surface. 

 Somewhat enlarged. 2. A side view of a gland. Much enlarged. 



3. A surface view of a gland. Much enlarged. 



larger rosettes, and in one case, on the uppermost 

 leaf of the smaller rosette, growing below and slightly 

 to the right of the larger rosette, the remains of a 

 moth are clearly seen. 



This plant has the power, not only of catching 

 small insects on its leaves, but of digesting and absorb- 

 ing them. What happens is briefly as follows. The 

 glandular hairs of the upper surface secrete a sticky 

 fluid, which attracts insects, probably under the 



