104 DROSERA ROTUNDIPOLIA. [Chap. VL 



spinach leaf, moistened with saliva, on a leaf of Drosera, and other 

 slices on damp cotton-wool, all exposed to the same teni|K'ruture. 

 After 10 hrs. the slice on the leaf of the Drosera was bathed in 

 much secretion from the inflected tentacles, and was now examined 

 under the microscope. No perfect grains of chlorophyll could be 

 distinguished; some were shrunken, of a yellowish-green colour, 

 and collected in the middle of the cells; others were disintegrated 

 and formed a yellowish mass, likewise in the middle of the cells. 

 On the other hand, in the slices surrounded by damp cotton-wool, 

 the grains of chlorophyll were green and as perfect as ever. My 

 son also placed some slices in artificial gastric juice, and these were 

 acted on in nearly the same manner as by the secretion. We have 

 seen that bits of fresh cabbage and spinach leaves cause the ten- 

 tacles to be inflected and the glands to pour forth much acid secre- 

 tion; and there can be little doubt that it is the protoplasm form- 

 ing the grains of chlorophyll, as well as that lining tne walls of 

 the cells, which excites the leaves. 



f^at and Oil. Cubes of almost pure uncooked fat, placed on 

 several leaves, did not have their angles in the least rounded. We 

 have also seen that the oil-globules in milk are not dig&sted. Nor 

 does olive oil dropped on the discs of leaves cause any inflection; 

 but when they are immersed in olive oil they become strongly in- 

 flected; but to this subject I shall have to recur. Oily substances 

 are not digested by the gastric juice of animals. 



Starch. Rather large bits of dry starch caused well-marked in- 

 flection, and the leaves did not re-expand until the fourth day ; but 

 I have no doubt that this was due to the prolonged irritation of 

 the glands, as the starch continued to absorb the secretion. The 

 particles were not in the least reduced in size; and we know that 

 leaves immersed in an emulsion of starch are not at all afl'ected. 

 I need hardly say that starch is not digested by the gastric juice 

 of animals. 



Action of the Secretion on Living Seeds. 



The results of some experiments on living seeds, selected by haz- 

 ard, may here be given, though they bear only indirectly on our 

 present subject of digestion. 



Seven cabbage seeds of the previous year were placed on the 

 same number of leaves. Some of these leaves were moderately, but 

 the greater number only slightly inflected, and most of them re- 

 expanded on the third day. One, however, remained clasped till 

 the fourth, and another till the fifth day. These leaves therefore 

 were excited somewhat more by the seeds than by inorganic ob- 

 jects of the same size. After they re-cxpandetl, the seeds were 

 placed under favourable conditions on damp sand ; other seeds of 

 the same lot being trie<I at the same time in the same manner, and 

 found to germinate well. Of the seven seeds which had been ex- 

 posc<l to the secretion, only three germinated ; and one of the three 

 seedlings soon perished, the tip of its radicle being from the first 



