ECOLOGY 639 
as bladder-like traps which allow the entrance but not the escape 
of small animals. Each of the traps represents a greatly 
modified, inflated leaf of vesicular form and usually about 1% to 
1g inch in diameter. From the margin of its opening project 
: 
Fic. 481.—A Bladderwort (Ultricularia Grafiana). Note the submerged stems 
bearing modified, bladder-like leaves. Small animals become entrapped in 
these bladders where they are decomposed and the water-soluble portions of their 
remains are absorbed as nourishment by the plant. In the lower right-hand cor- 
ner is a bladder-like leaf of another species (Utricularia neglecta) shown in section. 
The entrance to the bladder is protected by numerous hairs and by a trap door 
(t). Drawing based upon Kerner. (Gager.) 
stiff bristles. There is an upper and lower lip present. The 
lower lip is greatly thickened and provided with a cushion-like 
process that extends into the bladder. From the upper lip is 
suspended a thin elastic valve, the free edge of which rests upon 
the inner surface of the lower lip cushion and closes the opening. 
