Action of Glands. 521 



to plant movement, we owe to the researches of Darwin. They prove to 

 us the easy disposition of protoplasm to be moulded into such organic 

 structures under certain conditions. 



Insectivorous Plants. There are a good many plants that derive more 

 or less of their nourishment from animal food, and they are fitted out 

 with some special apparatus by which they are enabled to get its bene- 

 fit. The Pitcher Plant ( Sarracenia ), which is common in our swamps, 

 has leaves which are shaped like a deep, narrow cup. These leaves are 

 usually half full of water, which is pretty sure to contain a lot of 

 drowned insects. Their juices can hardly fail to be absorbed by the 

 plant, and so assist in its nourishment. This is rendered the more 

 probable from the fact that it is well settled that other plants do absorb 

 the juices of insects. 



The Utricularia, or Bladderwort, is usually a plant without roots, 

 floating in the water, but some land species have also been described, 



FIG. 244. 



FIG. 243. Branch of Utricularia nealecta, with di- 

 vided leaves, bearing bladders. 



FIG. 244. One of the Bladders of Utricularia neg. 

 lecta, showing the antennae and en trance underneatn. 



having roots by which they are attached 

 either to the soil or to other plants as 

 Fia. 243. epiphytes. Asa Gray describes thirteen 



American species, some of which are also found in Europe, and there are 

 many more foreign species. The peculiarity of the plant is the little 

 bladders ( titriculi ) which grow upon the leaves, generally near the base. 

 These bladders are translucent, of a greenish color, and when grown are 

 ^ of an inch in diameter in some species, and J. of an inch in others. 

 At the extremity of the bladder there is an opening or mouth, which is 

 closed by a valve opening inwards. This valve is a thin, transparent, 

 elastic flap, which is pushed in by minute crustaceans and infusoria as 

 they enter, but which immediately closing back against the lip of the 

 bladder, prevents them from returning. Around the mouth of the 

 bladder are a number of arms, or processes, resembling antennae, and 

 together with the general shape of the bladder, giving it the appearance 

 of a cypris or water-flea. . The interior walls of the bladder are covered 

 with little arms or processes, which Darwin calls quadrifid processes, 



