384 PINGUICULA VULGARIS. Chap. XVL 



acid secretion, but were not quite dissolved after two days ; and 

 the glands then began to dry. Nor could their complete dis- 

 solution have been expected from what we have seen with 

 Drosera. 



(11) Minute drops of skimmed m^7^ were placed on a leaf, and 

 these caused the glands to secrete freely. After 3 hrs. the milk 

 was found curdled, and after 23 hrs. the curds were dissolved. 

 On placing the now clear drops under the microscope, nothing 

 could be detected except some oil-globules. The secretion, 

 therefore, dissolves fresh casein. 



(12) Two fragments of a leaf were immersed for 17 hrs., 

 each in a drachm of a solution of airhonate of ammonia, of two 

 strengths, namely of one part to 437 and 218 of water. The 

 glands of the longer and shorter hairs were then examined, and 

 their contents found aggregated into granular matter of a 

 brownish-green colour. These granular masses were seen by 

 my son slowly to change their forms, and no doubt consisted of 

 protoplasm. The aggregation was more strongly pronounced, 

 and the movements of the protoplasm more rapid, within the 

 glands subjected to the stronger solution than in the others. 

 The experiment was repeated with the same result ; and on 

 this occasion I observed that the protoplasm had shrunk a little 

 from the walls of the single elongated cells forming the pedicels. 

 In order to observe the process of aggregation, a narrow strip 

 of leaf was laid edgeways under the microscope, and the glands 

 were seen to be quite transparent ; a little of the stronger solu- 

 tion (viz. one part to 218 of water) was now added under the 

 covering glass ; after an hour or two the glands contained very 

 fine gi-anular matter, which slowly became coarsely granular 

 and slightly opaque ; but even after 5 hrs. not as yet of a 

 brownish tint. By this time a few rather large, transparent, 

 globular masses appeared within the upper ends of the pedicels, 

 and the protoplasm lining their walls had shrunk a little. It 

 is thus evident that the glands of Pinguicula absorb carbonate 

 of ammonia ; but they do not absorb it, or are not acted on by 

 It, nearly so quickly as those of Drosera. 



(13) Little masses of the orange-coloured pollen of the 

 common pea, placed on several leaves, excited the glands to 

 secrete freely. Even a very few grains which accidentally foil 

 on a single gland caused the drop surrounding it to increase so 

 much in size, in 23 hrs., as to be manifestly larger than the 

 drops on the adjoining glands. Grains subjected to the secretion 

 for 48 hrs. did not emit their tubes; they were quite dis- 

 coloured, and seemed to contain less matter than before; that 



