Chap. VI. DIGESTION. 117 



The slices were not liquefied, for tlie walls of the cells, 

 composed of cellulose, are not in the least acted on 

 by the secretion. 



Pollen. — A little fresh pollen from the common pea 

 was placed on the discs of five leaves, which soon 

 became closely inflected, and remained so for two or 

 three days. 



The grains being then removed, and examined under 

 the microscope, were found discoloured, with the oil- 

 globules remarkably aggregated. Many had their 

 contents much shrunk, and some were almost empty. 

 In only a few cases were the pollen-tubes emitted. 

 There could be no doubt that the secretion had 

 penetrated the outer coats of the grains, and had 

 partially digested their contents. So it must be 

 with the gastric juice of the insects which feed on 

 pollen, without masticating it.* Drosera in a state of 

 nature cannot fail to profit to a certain extent by this 

 power of digesting pollen, as innumerable grains from 

 the carices, grasses, rumices, fir-trees, and other wind- 

 fertilised plants, which commonly grow in the same 

 neighbourhood, will be inevitably caught by the viscid 

 secretion surrounding the many glands. 



Gluten, — This substance is composed of two albu- 

 minoids, one soluble, the other insoluble in alcohol.f 

 Some was prepared by merely washing wheaten flour 

 in water. A provisional trial was made with rather 

 large pieces placed on two leaves ; these, after 21 hrs., 

 were closely inflected, and remained so for four days, 

 when one was killed and the other had its glands 

 extremely blackened, but was not afterwards observed. 



* Mr. A. W. Bennett found the Hort. Soc. of London,' vol. iv. 



undigested coats of the grains in 1874, p. 158. 

 the intestinal canal of pollen- f Watts' ' Diet, of Chemistry,' 



eating Diptera; see 'Journal of vol. ii. 1872, p. 873. 



