78 DROSERA ROTUNDIFOLIA. [Chap. VI. 



albumen had been given to this lea| than could be dissolved or 

 digested. 



Experiment S. Two cubes of albumen of ^ of an inch 

 (1.27 mm.) were placed on two leaves. After 40 hrs. every atom of 

 one was dissolved, and most of the liquefied matter was absorbed, 

 the fluid which remained being in this, as in all other cases, very 

 acid and viscid. The other cube was acted on at a rather slower 

 rate. 



Experiment Jf. Two cubes of albumen of the same size as the 

 last were placed on two leaves, and were converted in 50 hrs. into 

 two large drops of transparent fluid ; but when these were removed 

 from beneath the inflected tentacles, and viewed by reflected light 

 under the microscope, fine streaks of white opaque matter could 

 be seen in the one, and traces of similar streaks in the other. The 

 drops were replaced on the leaves, which re-expanded after 10 days; 

 and now nothing was left except a very little transparent acid 

 fluid. 



Experiment 5. This experiment was slightly varied, so that the 

 albumen might be more quickly exposed to the action of the secre- 

 tion. Two cubes, each of about ^ of an inch (.035 mm.) were 

 placed on the same leaf, and two similar cubes on another leaf. 

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

 rounded. After 40 hrs, the two cubes on the one leaf were com- 

 pletely liquefied, the fluid being perfectly transparent; 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 begin- 

 ning 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 recom- 

 menced. 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 digestion; and, secondly, whether 

 minute drops of weak hydrochloric acid, of the same strength 

 and size as those to be used, would injure the leaves. The 

 two following exi)eriments were therefore tried: 



Experiment 6. Small cubes of albumen were put on three 

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

 were sidded two or three times daily. These did not in the least de- 



