78 DROSERA ROTUNDIFOLIA. [Cuar. VI. 
the leaf re-expanded, but there was still left on the disc a minute bit 
of albumen now rendered transparent. More albumen had been given 
to this leaf than could be dissolved or digested. 
Experiment 3.—Two cubes of albumen of ṣẹ of an inch (1°27 mm.) 
were placed on two leaves, After 46 hrs. every atom of one was dis- 
solved, and most of the liquefied matter was absorbed, the fluid which 
remained being in this, as in all other cases, very acid and viscid. 
‘Lhe other cube was acted on at a rather slower rate. 
Experiment 4.—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 secretion. 
Two cubes, each of about =j; of an inch (*635 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 
46 hrs. the two cubes on the one leaf were completely 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 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 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 experiments 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 added 
two or three times daily. These did not in the least delay the process ; 
