94 DROSERA ROTUNDIFOLIA. Chap. VI. 



leaf. These were examined after 21 hrs. 30 m., and all four 

 were found roimdcd. After 46 hrs. the two cubes on the one 

 leaf were completely liquefied, the fluid being perfectly trans- 

 parent; on the other leaf some opaque white streaks could 

 still be seen in the midst of the fluid. After 72 hrs. these 

 streaks disappeared, but there was still a little viscid fluid 

 left on the disc; whereas it was almost all absorbed on the 

 first leaf. Both leaves were now beginning to re-expand. 



The best and almost sole test of the presence of 

 some ferment analogous to pepsin in the secretion 

 appeared to be to neutralise the acid of the secretion 

 with an alkali, and to observe whether the process 

 of digestion ceased ; and then to add a little acid 

 and observe whether the process recommenced. This 

 was done, and, as we shall see, with success, but it 

 was necessary first to try two control experiments ; 

 namely, whether the addition of minute drops of 

 water of the same size as those of the dissolved 

 alkalies to be used would stop the process of diges- 

 tion ; and, secondly, whether minute drops of weak 

 hydrochloric acid, of the some strength and size as 

 those to be used, would injure the leaves. The 

 two following experiments were therefore tried : — 



Eocperlment 6. — Small cubes of albumen were put on three 

 leaves, and minute drops of distilled water on the head of a pin 

 were added two or three times daily. These did not in the 

 least delay the process ; for, after 48 hrs., the cubes were com- 

 pletely dissolved on all three leaves. On the third day the 

 leaves began to re-expand, and on the fourth day all the fluid 

 was absorbed. 



Experiment 7.— Small cubes of albumen, were put on two 

 leaves, and minute drops of hydrochloric acid, of the strength of 

 one part to 437 of water, were added two or three times. This 

 did not in the least delay, but seemed rather to hasten, the 

 process of digestion ; for every trace of the albumen chsappeared 

 in 24 hrs. 30 m. After three days the leaves partially re- 

 expanded, and by this time almost all the viscid fluid on their 

 discs was absorbed. It is ahnost superfluous to state that 



