216 
3 days, a very slight and barely perceptible increase in thickness 
of from 5 to 15. 100% mm. (after 5 days 10 to 20. 100%: mm), 
and a slightly increased curvature, as compared with normal 
untouched hooks, is shewn. The difference is too slight to be 
satisfactory, and might be due to the manipulation, or to the 
drying up of the outer surface of the gelatine. More prolonged 
experiments could be made, and possibly definite results obtained, 
by means of the apparatus described by Pizrce'); but to set 
up, and maintain in working order, an apparatus of that kind 
in the open air, in the Tropics, during the rainy season, was 
a task of more difficulty, than at the time could successfully 
be accomplished. The question, therefore, as to whether without 
any “contact-stimulation” in the sense used by PrerrEr’), 4 
train on the hook tendril may cause it to thicken, is one 
which is still open, and which will apparently be finally 
answered in the affirmative. 
If a branch of Strychnos laurina fails to secure any support, 
it finally bends down towards the ground, the distal portion 
then growing upwards again. The hook-tendrils, borne at the 
bottom of the loop thus formed, are larger, of stronger growth, 
and when in contact, become thicker and stronger, than ordi- 
nary hooks do under maximal stimulation. This is probably 
due to the hook-tendrils receiving a better food supply and 
to the greater sap pressure, but, at the same time, the groales 
strength of such hooks is very useful in affording sufficient 
support for the erect growth of the elongating apical portion 
of the shoot. In all cases, the hook-tendrils, which a shoot, 
that has not succeeded in fixing itself to anything, finally 
produces, become, when attached, thicker than they do, when 
the branch has many and abundant attachments from the first, 
but here the difference is probably largely, or entirely, caused 
by the difference in the weight to be supported by each indi- 
vidual hook-tendril. 
1) Prence. Annals of Botany, Vol. VIII. No, XXIX. 1894, p. 66. reiiagees 
2) Zur Kenntniss der Kontaktreize, Untersuch aus dem Bot. Inst. zu 1u 
Bd. I, p. 483. 
