I will now give in detail my experiments on the digestive power of the secretion of Drosera, dividing the substances tried into two series, namely those which are digested more or less completely, and those which are not digested.  We shall presently see that all these substances are acted on by the gastric juice of the higher animals in the same manner.  I beg leave to call attention to the experiments under the head albumen, showing that the secretion loses its power when neutralised by an alkali, and recovers it when an acid is added.

Substances which are completely or partially digested by the Secretion of Drosera.

Albumen.—­After having tried various substances, Dr. Burdon Sanderson suggested to me the use of cubes of coagulated albumen or hard-boiled egg.  I may premise that five cubes of the same size as those used in the following experiments were placed for the sake of comparison at the same time on wet moss close to the plants of Drosera.  The weather was hot, and after four days some of the cubes were discoloured and mouldy, with their angles a little rounded; but they were not surrounded by a zone of transparent fluid as in the case of those undergoing digestion.  Other cubes retained their angles and white colour.  After eight days all were somewhat reduced in size, discoloured, with their angles much rounded.  Nevertheless in four out of the five specimens, the central parts were still white and opaque.  So that their state differed widely, as we shall see, from that of the cubes subjected to the action of the secretion.

[Experiment 1.

Rather large cubes of albumen were first tried; the tentacles were well inflected in 24 hrs.; after an [page 93] additional day the angles of the cubes were dissolved and rounded;* but the cubes were too large, so that the leaves were injured, and after seven days one died and the others were dying.  Albumen which has been kept for four or five days, and which, it may be presumed, has begun to decay slightly, seems to act more quickly than freshly boiled eggs.  As the latter were generally used, I often moistened them with a little saliva, to make the tentacles close more quickly.

Experiment 2.—­A cube of 1/10 of an inch (i.e. with each side 1/10 of an inch, or 2.54 mm. in length) was placed on a leaf, and after 50 hrs. it was converted into a sphere about 3/40 of an inch (1.905 mm.) in diameter, surrounded by perfectly transparent fluid.  After ten days 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 1/20 of an inch (1.27 mm.) were placed on two leaves.  After 46 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.