Botany and Zoology. 281 
ence in sensibility, I pony: 0388 loops of string of the same weight 
(in one instance weighing -82 of a grain) on the several lateral and on 
the terminal sub- polska ; in a few hours the latter were bent, but after 
- no effect was produced on any of the lateral petioles. Again,.a 
terminal sub-petiole placed in contact with a thin stick became sensibly 
curved in 45 m., and in 1 h. 10 m. had moved through ninety degrees, 
had elapsed. In this latter case, and in all other such cases, if pi sticks 
be taken away, the petioles continue to move during m hours after- 
ward; so they do after a ahs ubbing ; but sdeueeutakes if the flake 
ery great or ao PURE oe they become, after about a 
day’s interval, straight again.”—(p. 31. 
Tn rous cases, notably i in Salama ee the petiole when 
clasped i Increases very greatly in thickness and rigidity, undergoing a 
change in its woody structure by which the fibro- aabalet bundles, orig- 
inally semilunar in cross-section, develop into a closed ring, like that of 
an exogenous stem. 
hospermum scandens of the gardens — — its allies Mau- 
randia and Rhodochiton, by clasping Sinrcones ~ is plant, alone, 
€ young internodes are also sensitive to the ; : 
“When a petiole clasps a stick, it draws oe base of the internode 
is thus caught between the stem and the petiole as by a pair of joeiers 
- The internode straightons itself again, excepting the part in contact w 
the stick. Young internodes alone are sensitive, and these are aanitiie 
on all sides along” their whole length. I made ‘fifteen trials by lightly 
“mag two or three times with a thin twig several internodes; and in 
2h., but in one case in 3h, all became bent: they” became 
straight again in about 4h, subsequently. An internode, which was 
rubbed as much as six or seven times with a twig, a e just percepti- 
bly curved in 1h. 15 m., and subsequently in 3 . the curvature “ 
Here, then, is one case in which the sensibility of a stem is manifest, 
and a turned to useful sosdaat The peduncles of the allied Maurandia 
semperjflorens also sensitive and flexuous, although Mr. Darwin insists 
Guminose, Cucurbitacee and Cobea. And if twining stems in general 
are not endowed with “a dull kind of irritability,” as Mohl conjectured, 
it may well be because the equally wonderful automatic revolving move- 
ment leaves no need for it. - gene the most striking cases 
sete ste adet howerer whether answering to i or stem, 18 
OL. XL, No. 119.—Szpr., 
