REACTIONS OF TENDRILS OF AMPELOPSIS 27 



tests. Place pieces of rotten wood, boiled meat, or boiled egg, or 

 bits of glass no larger than a pin head on the tips of the glands 

 of tentacles at the margin of the 

 leaves. Observe the tentacles 

 with a lens and note the latent 

 period before movement is ob- 

 served, the period of curvature, 

 and the final position of the 

 stimulated organ. Does re- 

 laxation of the movement 

 occur while the object remains 

 on the tentacle ? Do all of the FlG . I2 . Xtiss^To? convex flank of 



objects mentioned secure equal tendril. B, of concave flank after forming 



reactions ? l loose coils - 



41. Contact Reactions of Tendrils of Ampelopsis. The branched 

 tendrils of Ampelopsis do not generally coil around supports. 

 These organs are fastened to solid objects by the tips which 

 undergo peculiar metamorphoses when they come in contact with 

 them. It is difficult to determine whether the resultant reaction 

 is due to a contact sufficiently strong to be called a pressure re- 

 action or not, but as has been noted the difference is not one of 

 quality, so that it may be taken up here. Examine the manner 

 in which an Ampelopsis is fastened to a wall. The tips are 

 found to be glued to the support, and are enlarged to form large 

 balls of tissue. If an unattached tendril is examined with the 

 microscope the transverse section will show a pith relatively large, 

 a circle of fibrovascular tissue, with large medullary rays extend- 

 ing from the pith to the cortex. A layer of collenchyma is pre- 

 sent in' the subepidermal layers of the cortex. Select young 

 tendrils or those recently fastened to a support and make out the 

 changes undergone by the tissues in forming the attachment. 2 



1 For changes in the tentacles during reaction see Huie, Quarterly Journal of 

 Microscopical Science, 39: — . 1896. 



2 Lengerkin, A. v. Die Bildung der Haftballen an den Ranken einiger Arten der 

 Gattung Ampelopsis, 43: 337, 353, 369, 385, 401. Bot. Zeitung. 1885. 



