ABSOEPTION OF FOOD MATEEIALS 149 



the roots of plants, so that the amount of the element which 

 is absorbed in such a way is very small. Indeed it may 

 be said that such an absorption is almost entirely excep- 

 tional. It has been found that plants are able to utilise 

 urea and other amides when these are present in the soil. 

 In very rich soils, or those containing a large quantity of 

 humus, such compounds are to be met with, and there is a 

 probability that they are more easily worked up into actual 

 nutritive substance than the inorganic compounds which 

 have been spoken of. 



A few plants obtain a more fully elaborated material in 

 a very different way. These are the so-called insectivorous 

 plants, which have the power of utilising proteid matters. 

 Among them may be mentioned the pitcher plants, 

 Nepenthes, Sarrdcenia, &c., and the fly-catching plants, 

 Drosera, Dioncea, and others. In the pitchers of Nepen- 

 thes, &c., which are specially modified foliar structures, 

 there is an accumulation of water, in which insects are 

 from time to time drowned. Their bodies decay, or are 

 digested by a peculiar secretion, which is prepared in the 

 tissue of the pitchers, and excreted into the water they 

 contain. The products of the decomposition or digestion 

 are absorbed by the tissue of the pitchers in the same way 

 as similar products are absorbed by the stomachs and 

 intestines of animals. Drosera and Dioncea bear certain 

 glandular structures on their leaves which pour out a fluid, 

 by which insects become surrounded after alighting on 

 the laminae. This secretion possesses digestive properties 

 resembling those of the gastric and pancreatic fluids of 

 animals, and by the action of this juice the bodies of the 

 captured insects are digested, and the nitrogenous material 

 is subsequently absorbed by the leaf surface. A fuller 

 discussion of these mechanisms will be found in a subse- 

 quent chapter. These plants are generally found growing 

 in such a situation that they are not brought into contact 

 with inorganic compounds of nitrogen, and hence are cut 

 off from the supplies which are afforded to the roots of 



