Chap. VI.] DIGESTION. 97 



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 na- 

 ture 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 albuminoids, 

 one soluble, the other insoluble in alcohol." Some was pre- 

 pared by merely washing wheaten flour in water. A pro- 

 visional trial was made with rather large pieces placed on two 

 leaves; these, after 21 hrs., were closely inflected, and re- 

 mained so for four days, when one was killed and the other 

 had its glands extremely blackened, but was not afterwards 

 observed. Smaller bits were placed on two leaves; these 

 were only slightly inflected in two days, but afterwai-ds be- 

 came much more so. Their secretion was not so strongly 

 acid as that of leaves excited by casein. The bits of gluten, 

 after lying for three days on the leaves, were more trans- 

 parent than other bits left for the same time in water. After 

 seven days both leaves re-expanded, but the gluten seemed 

 hardly at all reduced in bulk. The glands which had been 

 in contact with it were extremely black. Still smaller bits 

 of half putrid gluten were now tried on two leaves ; these 

 were well inflected in 24 hrs., and thoroughly in four days, 

 the glands in contact being much blackened. After five days 

 one leaf began to re-expand, and after eight days both were 

 fully re-expanded, some gluten being still left on their discs. 

 Four little chips of dried gluten, just dipped in water, were 

 next tried, and these acted rather differently from fresh 

 gluten. One leaf was almost fully re-expanded in three 

 days, and the other three leaves in four days. The chips 

 were greatly softened, almost liquefied, but not nearly all 

 dissolved. The glands which had been in contact with them, 

 instead of being much blackened, . were of a very pale col- 

 our, and many of them were evidently killed. 



' Mr. A. W. Bennett fonnd nal of Hort. Soc. of London,' 



the nndlgcHted conta of the vol. Iv. 1874. p. LVi. 

 grnlns In the Inteslinnl canal of ' Watts' ' Diet, of Chemistry,' 



pollen-eating Dlptera; see 'Jour- vol. li. 1872, p. 873. 



