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A tendril, coiled around two stems 0.5'cm. diam. and 3 cm. apart, 
became at the first point of contact (2) 470 490 in thickness , 
the intermediate portion (4) being 355 290, at (c) the distal 
point of contact, where one complete coil is formed, being 550 ; 400. 
The thicknesses of corresponding points on the opposite unat- 
tached tendril were (a) 240 ; 165 (0) 365 165 (c) 335 : 195. 
It follows therefore, that a contact stimulus of local application 
does not transmit an equal effect to all parts of the tendril 
but is largely localized around the points immediately in 
contact. 
The attachment of a small loose twig to the tendril is suf- 
ficient to cause coiling and thickening, but if too thin and 
light the stimulus may be a subminimal one. 
8 Mal so ag 9 pgere coils. 
V shaped piece of wood 3 mm. diam. and 1 grm. 
weight attached for 2 weeks. 320 . 200 . 12/3; 280 . 100 . 11/3. 
V shaped piece of wood 2 mm. diam. and 1/, grm. 
weight attached for 2 weeks. 315 . 180. 1/,; 290 . 145 . 1'/,. 
A piece of wood less than 2 mm. diam. and | grm. weight 
acts as a subminimal stimulus. As in Sérychnos, rubbing the 
irritable concave surface at intervals, during a quarter of an 
hour several times daily, produces after 3 days a distinctly 
increased curvature, but no, or only a very slight, increase in 
thickness as compared with normal untouched tendrils. 
Another interesting transition form is afforded by the tendrils 
of Vitis discolor, in which a slight increase of thickness may 
be seen in the diameter of the wood cylinder, when permanently 
attached to a fixed support. The tendrils of V. discolor are long 
and slender with a short terminal unbranched portion, separated 
from the basal portion by a scaly rim. The terminal portion 
is the most irritable, the basal portion being only slightly 
irritable to even prolonged contact. The former, when in con- 
tact, commences to curve in | hour, and in 3 may describe 
an are of 110° to 180°. If the tendril is placed in alcohol as 
soon as the curvature has become at all marked, the latter 
