OF THE LEGUMES OF PENTACLETHRA MACROPHYLLA. 419 
longer transverse diameter perpendicular to the inner surface of the valve,—the inner- 
most cells of the contractilelayer being generally considerably larger than the outer ones 
of the same layer, and not so much thickened in proportion to their size by secondary 
deposits. Two narrow strips were cut out of a valve, and of its entire thickness—one 
parallel to the length of the cells of the contractile tissue, the other nearly at right 
angles and transverse to their length. The former scarcely gained an appreciable 
amount on soaking; the latter gained about one-third of a line, or 4st of its length. 
Fig. 8 represents a section of a similar valve of the Common Pea, the prosenchymatous 
cells (more highly magnified in fig. 9) being cut transversely. The proportion of thin- 
walled cellular tissue in this valve is large. Seeing, from these instances, that in numerous 
legumes the principal contraction of the valves is in the direction of the breadth of the 
cells of the contracting layer, there is no reason why, in the case of the Orotalaria 
referred to above, the contraction of the opposing layers may not also be transverse. In 
this partieular case, however, whether the contraction be in the direction of the length 
or of the breadth of the cells, the result must be the same. 
I have no observations to record upon the behaviour of the hygroscopic tissue of these 
legumes with reagents. Under the microscope the secondary thickening layers of the 
cells do not present any peculiarity further than a horny consistence, characteristic of 
some so-called collenchymatous, and also of certain liber cells. 
Some reference was made, orally, at the Meeting at which this Note was laid before the 
Linnean Society, to the observations of the late Robert Brown upon the spiral twisting 
of the fruits of certain Cyrtandracez, and to the twisting &c. of the fruits of some other 
Orders, but I do not consider it needful to reproduce these references here. ; 
Mr. Darwin has kindly directed my attention to a short memorandum by Mr. Wyman, 
in the <“ Proceedings of the American Academy ’ (vol. iii. p. 167), of observations upon 
the contractility of the valves of the fruit of Balsams, and of Echinocystis lobata, a 
Cucurbitaceous plant. Mr. Wyman concludes that, in these plants, *the motion is due 
to the spontaneous contraction of the cells on the contracting side, in the way that 
motion is produced in the hydroid polyps. In the contracted capsule the cells on the 
concave side are found to be shortened, while those on the opposite side are elongated. 
In the Balsam capsule the contraction is so sudden that the shortening of the cells cannot 
be watched; but in the Echinocystis the motion is so gradual that the change can be 
observed under the microscope. When gradually subjected to the action of anzesthetic 
agents the capsules lose their contractility; but when suddenly placed under their 
influence an immediate contraction is the usual result.” The mechanism of contraction 
in the case of the plants observed by Mr. Wyman is wholly different from that which I 
have described above. The entire subject deserves more attention than it has as yet 
received. 
