Chap. XVI.] SECRETION, ABSORPTION, DIGESTION. 311 



r^ret that I did not try this substance after having been im- 

 mersed in weak hydrochloric acid, as it would then probably have 

 been quickly dissolved. 



(9) A siiiail square thin piece of pure gelatine, moistened with 

 water, was placed on a leaf, and excited very little secretion in 5 

 hrs. 30 ni., but later in the day a greater amount. After 24 hrs. 

 the whole square was completely liquefied; and this would not 

 have occurred had it been left in water. The liquid was acid. 



(10) Small particles of chemically prepared casein excited acid 

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

 glands then began to dry. Nor could their complete dissolution 

 nave been expected from what we have seen with Drosera. 



(11) Minute drops of skimmed milk 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 carbonate of ammonia, of two 

 strengths, namely of one part to 347 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 re- 

 peated 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 pro- 

 cess of aggregation, a narrow strip of leaf was laid edgewaj's under 

 the microscope, and the glands were seen to be quite transparent; 

 a little of the stronger solution (viz. one part to 218 of water) 

 was now added under the covering glass; after an hour or two 

 the glands contained very fine granular matter, which slowly be- 

 came 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 appearc<l within the upper ends of 

 the piedicels, 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 le.nves, excitetl the glands to secrete freely. 

 Even a verj' few grains whit-h accidentally fell 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 discoloured, and seeme<l to contain 

 less matter than before; that which was left being of a dirty col- 



