OF INSECTIVOROUS PLANTS 421 



Hooker (2) found that the pitcher Hquor was ahvays acid. The 

 secretion of the hquor was not increased b}' the introduction of inorganic 

 substances, but was increased by the introduction of animal matter into 

 the pitcher. As substrates, Hooker used fibrin, raw meat, cartilage and 

 cubes of egg white. He reported: — 



"After twenty-four hours' immersion, the edges of the cubes of white 

 of egg are eaten away, and the surfaces gelatinised. Fragments of meat 

 are rapidly reduced; and pieces of fibrin weighing several grains dissolve 

 and totally disappear in two or three days. With cartilage the action 

 is most remarkable of all; lumps of this weighing 8 or 10 grains are half 

 gelatinised in twenty-four hours, and in three days the whole mass is 

 greatly diminished, and reduced to a clear transparent jelly. After 

 drying some cartilage in the open air for a week, and placing it in an 

 unopened but fully formed pitcher of A\ Rafflesiana, it was acted upon 

 similarly and very little slower. " 



All of the above experiments save the last were apparently conducted 

 in opened pitchers. Experiments, made in vitro with pitcher liquor and 

 fibrin, meat, and cartilage, gave a digestion of the substrates "wholly 

 different" from that occurring in the pitchers. Hence the digestive 

 action in the pitchers was not produced by the fluid first secreted by the 

 pitchers. 



From these and similar experiments Hooker concluded: — "It would 

 appear probable that a substance acting as pepsine is given off from the 

 inner wall of the pitcher, but chiefly after placing animal matter in the 

 acid fluid; but whether this active agent flows from the glands or from 

 the cellular tissue in which they are imbedded, I have no evidence to 

 show. " However, he attributed all three phenomena — secretion of the 

 acid liquor, digestion (secretion of the digestive enzyme), and assimila- 

 tion — to the glands, and decided that Nepenthes possess a true digestive 

 process. 



From the following experiments, it seemed probable that the tempera- 

 ture influenced the digestive action. When cartilage or fibrin was kept 

 for six days in pitchers of N. ampullaria in a cold room, it was not di- 

 gested; the substrate, however, was immediately acted upon when trans- 

 ferred to pitchers of N. Rafflesiana in a stove house. 



If large amounts of substrate were introduced into a pitcher, digestion 

 and absorption did not attain completion, and putrefaction was noted 

 after the lapse of many days. 



Tait (3) isolated an enzyme from the liquor of unopened Nepenthes 

 pitchers, and also from the liquor of opened pitchers. His procedure 



