EXTRACTS FROM FOREIGN PERIODICALS. 200 
tenuity, and intermixed with globules disposed in longitudinal series. A blade 
raised longitudinally upon this fibrous tissue being plunged into aerated water, 
directed its curvature towards the centre of the petiole; if this blade be placed 
in non-aerated water, it will not curve at all. Thus this fibrous tissue is 
incurvable by oxygenation; under this is found a woody substance with medul¬ 
lary rays, and principally composed of sap-vessels and of a considerable quantity 
of large pneumatic tubes. In the centre of the petiole there is a bundle of fibrous 
tissue similar to that described above, and taking the place of the pith in this 
petiole which represents a little stalk. When this is exposed, we find that the 
petiolary bending of the leaflet of the Kidney-bean contains the two incurvable 
tissues which I have already described in flowers capable of closing after expansion, 
namely, the cellular tissue incurvable by endosmose, and the fibrous tissue in¬ 
curvable by oxygenation. The two cylindrical layers inclosed one in the other 
which form these two tissues, would be represented sufficiently accurately by 
the reunion and attachment in a cylindrical bundle of a certain number of nerves 
of the flower of Mirabilis. I have pointed out, that near these nerves the 
cellular tissue curves outwards by endosmose, and that the fibrous tissue curves 
inwardly by oxygenation ; which produces in the first case their state of expan¬ 
sion, and in the second that of sleep. The same would happen in the petiolary 
curvature of the leaflet of the Kidney-bean, if we suppose that the two 
cylindrical layers, the one exterior to the cellular tissue, the other interior to the 
fibrous tissue, are divided at the same time into fine longitudinal bundles. Each 
of these bundles is analogous to a nerve of the flower of Mirabilis; there will be 
in it, and arranged in this nerve, the two incurvable tissues capable of effecting 
the expansion and the closing. Supposing these bundles reunited by a mem¬ 
branous tissue, that would form a corolla susceptible, by turns, of expansion and 
closing, or of waking and sleeping. But this state of separation of longitu¬ 
dinal fascise does not exist in the petiolary curvature; these fictitious fasciae 
are intimately united, and form a hollow cylinder composed of two layers ; 
the cylindrical layer of fibrous tissue is inclosed in the cylindrical layer of 
cellular tissue. Let us suppose each of these cylindrical layers divided into 
longitudinal threads, joined to each other. The longitudinal threads of cellular 
tissue would dispose all to direct their curvature outwards. Now it is evident, 
that if their power of incurvation is equal, the cylindrical layer which they 
form by their junction will remain straight and equal; but if the longitudinal 
threads of one side of the cylinder force it by the power of incurvation to' the 
threads of the opposite side, these would be impelled in the direction of incurva¬ 
tion effected by the threads which antagonise them. The same reasoning may 
be employed in'relation to the cylindrical layer of fibrous tissue subjacent to 
the cylindrical layer of cellular tissue; thus each of these cylindrical layers 
2 F 
VOL. III.—NO. XIX. 
