76 LEAF-CLIMBEKS. Chap. II. 



portion of the petiole can seize a support. I have 

 seen a substance as soft as a withered blade of grass 

 caught. Petioles which have clasped any object 

 ultimately become rather thicker and more cylindri- 

 cal. On lightly rubbing several petioles with a twig, 

 they became perceptibly curved in 1 hr. 15 m., and 

 subsequently straightened themselves. A stick gently 

 placed in the angle between two sub-petioles excited 

 them to move, and was almost clasped in 9 hrs. A 

 loop of thread, weighing one-eighth of a grain, caused, 

 after 12 hrs. and before 20 hrs. had elaj)sed, a consider- 

 able curvature ; but it was never fairly clasped by the 

 petiole. The young internodes are in continual move- 

 ment, which is considerable in extent, but very irregu- 

 lar ; a zigzag line, or a spire crossing itself, or a figure 

 of 8 being formed. The course during 12 hrs., when 

 traced on a bell-glass, apparently represented about 

 four ellipses. The leaves themselves likewise move 

 spontaneously, the main petioles curving themselves 

 in accordance with the movements of the internodes ; 

 so that when the latter moved to one side, the petioles 

 moved to the same side, then, becoming straight, 

 reversed their curvature. The petioles, however, 

 do not move over a wide space, as could be seen when 

 a shoot was securely tied to a stick. The leaf in this 

 case followed an irregular course, like that made by 

 the internodes. 



Adlumia cirrhosa. I raised some plants late in the 

 summer ; they formed very fine leaves, but threw 

 up no central stem. The first-formed leaves were not 



