IRREGULAR NUTRITION 



209 



side by a downward drooping hood, which effectually prevents its use 

 as a step in climbing up out of the fluid. Hooker showed in 1874 that 

 the fluid within was capable of dissolving white-of-egg. It appears 

 that here also the absorption of some digested 

 matter is necessary before the ferment is 

 secreted in quantity. The ferment is of the 

 tryptic type, for it has been shown that it 

 is able to break down digested proteids into 

 the state not only of peptone, but in part 

 to the state of amide crystalline bodies. In 

 this form they are readily absorbed by the 

 plant, which thus receives a supply of com- 

 bined nitrogen, as well as of certain mineral 

 salts. In the somewhat similar, though 

 morphologically quite distinct urns of Sarra- 

 cenia and Cephalolus, ferments have not been 

 demonstrated. Nor have they in the smaller 

 traps of Utricularia, though glandular hairs 

 are present on their inner surface. But this 

 is not surprising since the urns are commonly 

 sunk in water or in mud, and the presence 

 of water inside them would interfere with 

 the necessary tests. 



The extraordinary forms and mechanisms 

 thus seen in carnivorous plants seem to 

 accentuate the importance for them of the 

 gain which follows on this accessory nutri- 

 tion. Yet all of these plants can live 

 without it, while a surfeit of animal food may be experimentally 

 shown to be harmful to them. These plants stand out as some of the 

 strangest results of special adaptation, and strike the observer as 

 showing a grotesque disproportion between the end gained and the 

 means adopted to secure it. 



FIG. 158. 



Pitcher of Nepenthes, with part 

 of the wall removed to show the 

 fluid (F) secreted by the glands 

 borne on the inner surface, 

 (i natural size.) (After Stras- 

 burger.) 



Thus many plants, and often those in which we should least expect 

 it, have other methods of nutrition than the autotrophic process. 

 The degree of dependence upon irregular methods varies greatly. 

 The habit is not restricted to any one family or group of 

 plants. It has been seen that sometimes single species or genera, 

 sometimes whole families are affected. These phenomena are 

 chiefly found in advanced families such as Leguminosae, Orchids, 



B. 11. O 



