78 BOTANY. [CHAP. n. 



interesting to note that a substance called rennet, con- 

 sisting of portions of calves' stomachs, is still used for a 

 similar purpose, its efficacy being also due to the presence 

 of gastric juice. In Utricularia or bladder wort, the 

 plants are aquatic and rootless, and the much cut leaves 

 bear several little bladders that act as traps to water- 

 fleas and other minute aquatic animals. Finally, in 

 many exotic species, popularly known as pitcher plants, 

 certain of the leaves are modified into hollow pitcher- 

 like receptacles specially arranged for the capture of 

 insects, or, in some species where the pitchers are large, 

 of humming birds or small animals. In the species of 

 Sarracenia, inhabiting the turfy, spongy bogs of America, 

 the pitcher- shaped leaves are very effective fly-traps. A 

 sugary juice is secreted round the mouth of the pitcher 

 that attracts insects, which descend lower in the tube, 

 and are precipitated into a watery secretion filling the 

 bottom of the pitcher, their egress being prevented by a 

 ring of reflexed hairs. The walls of the lower portion of 

 the inside of the pitcher are lined with glands that 

 secrete a digestive fluid that mixes with the water in the 

 pitcher. 



Parasites and Saprophytes. The foregoing remarks 

 respecting the nutrition of plants and their influence on 

 surroundings, applied solely to what may be termed 

 typical plants ; that is, plants developing chlorophyll, 

 which embraces the great bulk of the members of the 

 vegetable kingdom. There are, however, a very large 

 number of true plants that never develop chlorophyll, 

 and consequently cannot assimilate inorganic matter as 

 food, but, like numbers of the animal kingdom, require 

 organic food. Such plants fall naturally under two 



