MOTIONS IN PLANTS. 
a73 
They are always marked and outlined by the spiral wire : what, 
then, but its contraction can guide those plants, and preserve 
those folds, in the admirable order in which they are laid ? 
View the stapelia, particularly the cavipanulata. Could any 
thing but this muscle preserve this washy corolla in such ad- 
mirable order, and arrange its pointed tops so even and exact 
when going to close ; or could any power but the spiral shut the 
petals of the asclepias variagata one by one, and fold them 
down With the same spring observed in the muscles ? But it is 
in vain thus to multiply evidence j not a single motion of a leaf 
or corolla (if watched with care, and minutely examined) 
that is not move convincing than all ! can write on the subject. 
Tlie purpose of this letter is merely to point them out, and en- 
dfiicc. 
deavour to prevail on botanists to seek them, I dare not ha- 
zard at once to show all that may be known of their mecha- 
nical powers, but would fain tempt a more philosophical me~ 
ckanic, and a better chemist, to view what a plant (^tvcll dissect- 
ed) will present to the astonished senses, and then to explain it 
better than I can. 
1 have shown, that in all plants that rise from the ground 
spiral wire cn 
yearly, the spiral runs next the alburnum at the exterior of the twiniugpl.mt*, 
wood, instead of within it, as in trees. Now, in all twining 
plants much motion is requisite, anti therefore w’heii dissected, 
a superabundance of the muscles are discovered. Indeed, the 
tendril is formed of little else ; but to be assured of this, it 
must be taken entirely to pieces, for they are all concealed in 
their cases ; these must be laid open ere the interior can be 
developed j then the tendrils will be found loaded with them. 
'1 he letter given by Mr. Knight, in the Philosophical Trans- 
actions, is, in every respect, most admirable, except in the 
ciu.se to which he attributes the motion, which I c.annot (though 
with all the humility neces.sary in venturing to differ from so 
great a man) help controverting. It is his opinion, that the Supposed 
twisting of the tendril is caused by the pressure of the stick on of 
the side of the tendril, which, driving the juices to the con- ttuJrils. 
trary side, swells the opposite part, and thus turns it. Now, 
if the juices could change their situation, I caunot conceive 
. that 
