The backs of the leaves bear numerous minute papillae, which do not secrete, but have the power of absorption.  These papillae are, I believe, rudiments of formerly existing tentacles together with their glands.  Many experiments were made to ascertain whether the backs of the leaves could be irritated in any way, thirty-seven leaves being thus tried.  Some were rubbed for a long time with a blunt needle, and drops of milk and other exciting fluids, raw meat, crushed flies, and various substances, placed on others.  These substances were apt soon to become dry, showing that no secretion had been excited.  Hence I moistened them with saliva, solutions of ammonia, weak hydrochloric acid, and frequently with the secretion from the glands of other leaves.  I also kept some leaves, on the backs of which exciting objects had been placed, under a damp bell-glass; but with all my care I never saw any true movement.  I was led to make so many trials because, contrary to my previous experience, Nitschke states* that, after affixing objects to the backs of leaves by the aid of the viscid secretion, he repeatedly saw the tentacles (and in one instance the blade) become reflexed.  This movement, if a true one, would be most anomalous; for it implies that the tentacles receive a motor impulse from an unnatural source, and have the power of bending in a direction exactly the reverse of that which is habitual to them; this power not being of the least use to the plant, as insects cannot adhere to the smooth backs of the leaves.

I have said that no effect was produced in the above

* ‘Bot.  Zeitung.’ 1860, p. 437. [page 232]

cases; but this is not strictly true, for in three instances a little syrup was added to the bits of raw meat on the backs of leaves, in order to keep them damp for a time; and after 36 hrs. there was a trace of reflexion in the tentacles of one leaf, and certainly in the blade of another.  After twelve additional hours, the glands began to dry, and all three leaves seemed much injured.  Four leaves were then placed under a bell-glass, with their footstalks in water, with drops of syrup on their backs, but without any meat.  Two of these leaves, after a day, had a few tentacles reflexed.  The drops had now increased considerably in size, from having imbibed moisture, so as to trickle down the backs of the tentacles and footstalks.  On the second day, one leaf had its blade much reflexed; on the third day the tentacles of two were much reflexed, as well as the blades of all four to a greater or less degree.  The upper side of one leaf, instead of being, as at first, slightly concave, now presented a strong convexity upwards.  Even on the fifth day the leaves did not appear dead.  Now, as sugar does not in the least excite Drosera, we may safely attribute the reflexion of the blades and tentacles of the above leaves to exosmose from the cells which were in contact with the syrup, and their consequent contraction.  When drops of syrup are placed on