Chap. X.] SENSITIVENESS OF THE LEAVES. 189 



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 move- 

 ment, 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 

 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 foot-stalks 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 up- 

 wards. 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 the leaves of plants with 

 their roots still in damp earth, no inflection ensues, for the 

 roots, no doubt, pump up water as quickly as it is lost by 

 exosmose. But if cut-off leaves are immersed in syrup, or in 

 any dense fluid, the tentacles are greatly, though irr^ularly, 

 inflected, some of them assimiing the shape of corkscrews; 



Bot. Zeltung,' 18C0, p. 377. 



