346 ASSIMILATION. 



lapping margin which had been brought into contact with the 

 flies, were all secreting copiously." ^ 



The incurvation lasts for onl}- a day or two, after which the 

 leaf assumes its former position : fragments of glass keep the mar- 

 gins incurved for a shorter time than do nitrogenons bodies.^ 



907. Darwin snggests the two following advantages which 

 the plant can derive from even tliis transient inrolling: (1) 

 the captured food and the secretion are protected from rain, 

 and (2) the food is brought into contact with a larger number 

 of glands than if the leaf remained flat. 



908. It appears probable that the leaves of Pingnicula derive 

 some nourishment from the seeds, etc., which may fall upon them. 

 "We may therefore conclude that Pingnicula vulgaris, with its 

 small roots, is not onlj- supported to a large extent by the extraor- 

 dinarj' number of insects which it habitually captures, but like- 

 wise draws some nourishment from the pollen, leaves, and seeds 

 of other plants which often adhere to its leaves. It is therefore 

 partlj' a vegetable as well as an animal feeder." ' 



909. Utricniaria, a genus named from the utriculi or little 

 bladders found on the dissected leaves of some of its species, 

 belongs to the same natural order as Pingnicula. Its members 

 capture minute aquatic animals by means of peculiar traps. 

 Each bladder has at its mouth a few diverging hairs, while just 

 within the orifice there is a sort of trap-door, which can be lifted 

 bj' a slight touch and then falls b}' its own weight, covering the 

 mouth and preventing egress. If a small aquatic animal passes 

 through the entrance and pushes by the funnel-shaped trap-door, 

 it is securely' imprisoned. The interior of the bladders is lined 

 more or less tbickl}- with peculiar glandular hairs not very unlike 

 those intermingled with the glands of Drosera, and found also on 

 the valves of Dionsea. These are either bifid or quadrifid. 



910. According to Darwin these hairs have the power of ab- 

 sorbing dissolved matters in a state of decay, but there is in 

 them no true digestive capacit}-. If the plants can utilize ani- 

 mal matter at all, it is onl3' after it has become dissolved during 

 the process of decay. 



911. Gcnlisea. The plants belonging to the genus Genllsea 

 — a genus allied to Utricularia — have two kinds of leaves, ordi- 

 nary and bladder-bearing, and the bladders have something of 

 the same arrangement at the orifice as has already been alluded 

 to under Utricularia. 



' Insectivorous Plants, p. 371. ' Insectivorous Plants, p. 390. 



" Insectivorous Plants, p. 377. 



