148 SourH AFRICAN BOTANY 
but docs not close. On the mner side of the pitcher are 
downward pointing hairs, and at the bottom is « fluid, 
and the insects slip down the sides, fall into the liquid, 
and are drowned, and then digested. Dionsa, Pingui- 
cula, and Utricularia are other insectivorous plants which 
exhibit different mechanisms for the capture of their 
prey. Dionza, which grows in the peat-bogs of North 
Carolina, captures insects by the sudden closing of the 
two halves of a leaf. Pinguicula has sensitive leaves, 
the inargins of which close over the captured insect. 
Utricularia is an aquatic plant, growing in small pools, 
and small green bladders are found in some of its leaves. 
In each bladder there is a small valve, which only opens 
inwards. Minute water animals, snails, etc., can easily 
pass into this opening, but cannot get out again. They 
are then absorbed by the plant by means of the digestive 
juices inside the bladder. 
Tor Puant anp Its ENVIRONMENT. 
122. Irritability.—Protoplasm has the power of being 
stimulated by outside influences and of making a cer- 
tain response to them. This property of protoplasm is 
known as IRRITABILITY, and is most important to the 
plant, as by this means it is brought into harmony with 
its surroundings. The growing parts of plants exhibit 
' this property more than the mature organs, but in some 
cases the mature organs will show movement in response 
to a stimulus. 
123. Stimuli.—A StimuLus denotes any outside in- 
fluence which excites a response on the part of the 
plant. The chief stimuli are light, gravity, moisture and 
