Chap. XVI.] MOVEMENTS OP THE LEAVES. 305 



We learn from the foregoing experiments that the mar- 

 gins of the leaves curl inwards when excited by the mere 

 pressure of objects not yielding any soluble matter, by ob- 

 jects yielding such matter, and by some fluids namely an 

 infusion of raw meat and a weak solution of carbonate of 

 ammonia. A stronger solution of two grains of this salt to 

 an ounce of water, though exciting copious secretion, paraly- 

 ses the leaf. Drops of water and of a solution of sugar or 

 gum did not cause any movement. Scratching the surface 

 of the leaf for some minutes produced no effect. Therefore, 

 as far as we at present know, only two causes namely slight 

 continued pressure and the absorption of nitrogenous matter 

 excite movement. It is only the margins of the leaf which 

 bend, for the apex never curves towards the base. The pedi- 

 cels of the glandular hairs have no power of movement. I 

 observed on several occasions that the surface of the leaf be- 

 came slightly concave where bits of meat or large flies had 

 long lain, but this may have been due to injury from over- 

 stimulation.* 



The shortest time in which plainly marked movement was 

 observed was 2 hrs. 17 m., and this occurred when either 

 nitrogenous substances or fluids were "placed on the leaves; 

 but I believe that in some cases there was a trace of move- 

 ment in 1 hr. or 1 hr. 30 m. The pressure from fragments 

 of glass excites movement almost as quickly as the absorp- 

 tion of nitrogenous matter, but the degree of incurvation 

 thus caused is much less. After a leaf has become well in- 

 curved and has again expanded, it will not soon answer to a 

 fresh stimulus. The margin was affected longitudinally, up- 

 wards or downwards, for a distance of .13 of an inch (3.302 

 mm.) from an excited point, but for a distance of .46 of an 

 inch between two excited points, and transversely for a dis- 

 tance of .2 of an inch (5.08 mm.). The motor impulse is not 

 accompanied, as in the case of Drosera, by any influence 

 causing increased secretion; for when a single gland was 

 strongly stimulated and secreted copiously, the surrounding 

 glands were not in the least affected. The incurvation of 

 the margin is independent of increased secretion, for frag- 



* [Bfltnlln (' Flora.' 1887) be- by nctnnl growth, and thiiR a 



lleves that the depresHiona are permanent alteration In the form 



due to the fact that the curva- of the leaf is effected. F. D.J 

 ture of the leaf Is accompanied 



