17 



nitrogen — cartilage for example. As in animals, these ])laiiis 

 carry on digestion by means of an acid and a ferment. Two 

 ferments have been discovered in insectivorous plants, " Droserin," 

 •which is analagous to the pepsine of the stomach, and " Azerin," 

 "which is analagous to the ptyalin of the saliva. 



In the " Bladderwort," or Utricidaria, ■which is an ai|uatic 

 plant, a number of little cells or bladders are attached to the 

 leaves. Each cell has an opening, -which is closed by a tiny 

 valve, which is transparent and colourless, and very flexible and 

 •elastic. "When a small animal, such as an Entomostracous 

 Crustacean, enters the bladder, the valve closes the cell at the 

 •orifice, and entraps the animal. Larvae, worms, and even newly- 

 hatched fishes are found in the Utricularia. The captured animals 

 die from loss of oxygen, and the plants absorb the products of 

 decay. 



The Droseracece are a family composed of only six genera, 

 -all of which agree in being insectivorous, though they, diflfer 

 greatly among themselves in the mode of capturing and utilising 

 animal food. The Drosera, or Sundew, is a genus containing 

 a large number of species, which are spread all over the world. 

 The leaves are covered with tentacles, and at the tip of each 

 tentacle is a gland which secretes the viscid matter. "When an 

 insect alights on the tentacles, these begin to curve in towards 

 the centre of the leaf. The animal is firmly grasped, and escape is 

 hopeless. An extremely minute stimulus is able to bring about 

 this motion — a piece of human hair one millionth of a grain in 

 weight is sufficient. Darwin found that of a large number of 

 fluids containing Nitrogen a very minute quantity indeed is 

 sufficient to produce the efi'ect — as, for example, the one-twenty 

 millionth of a grain of phosphate of ammonia. 



The Dionaea, or Venus's Flj'-trap, is found in North Carolina. 

 The leaf is in two halves, which are capable of being folded 

 like the leaves of a book, and it is suiaplied with filaments, which 

 are endowed with irritability. "When an insect alights upon 

 and comes in contact with the filaments, the leaf closes upon 

 it like a rat-trap. By an experiment of Dr. Sanderson's, it was 

 shown that an electric cuiTent passes through the leaf of the 



