OF THE LEGUMES OF PENTACLETHRA MACROPHYLLA. 417 
From these memoranda, it appears that the average increase in length of the prosen- 
chymatous bundles, when soaked in water, amounts to about 16 per cent., so that the 
bundles of an entire valve, 20 inches in length, may be supposed to contract or lengthen 
to an extent of 3 inches, or a little over. This amount of difference in length on con- 
tracting abundantly suffices to explain the insubordination manifested by the legumes 
when strapped down upon boards for exhibition in the Museum. 
Microscopic examination of a transverse section of one of the valves shows the con- 
tracting, hygroscopie bundles of prosenchymatous tissue, imbedded in a thin-walled, often 
coloured parenchyma, which may be compressed or drawn out by the contraction or 
dilatation of the bundles which it surrounds. This parenchyma cannot interfere, to any 
material extent, with the action of the bundles. 
The prosenchymatous cells are usually very thick-walled and pale-coloured. Fig. 5 
represents some bundles of the contracting tissue in cross section, with their surrounding 
parenchyma; fig. 7 the same in longitudinal section; fig. 6 is a portion of the prosen- 
chyma in cross section, highly magnified, showing the canals of the secondary, somewhat 
horny layers, and their concentrie lamination, similar to that often found in thick-walled 
cells, 
T accompany the drawings of the contracting tissues of Pentaclethra by diagrams of the 
corresponding tissues in the legumes of Phanera Vahlii, Crotalaria incana, the common 
Pea (Pisum), and a Lathyrus. In the valves of these legumes the principal layer (or 
layers) of contractile tissue is continuous (that is, it is not broken up into distinct bundles, 
as in Pentaclethra) and oblique to the valve; but its action appears to be controlled, in the 
Phanera and Crotalaria, by other layers of prosenchyma, either hygroscopic, and capable, 
more or less, of partial extension and contraction, or neutral. The valves of the Phanera 
are about 8 to 12 inches in length, about 23 inches broad, and 1j to 2 lines in thickness. 
When mature and dry they are very rigid, and spirally curved inwards. They snap 
obliquely in a direction transverse to their contraction, and parallel to the prosenchy- 
matous cells of the innermost woody layer of the valve. Fig. 11 represents a transvérse 
section of a valve cut at right angles to the direction of its contraction. The innermost 
layer (a) consists of thick-walled prosenchyma, capable of but very slight extension when 
moistened. A strip, 1 inch in length, cut out of this innermost layer parallel, or nearly 50, 
to the direction of its cells (the tissue of the second layer being removed by a knife as far 
as could easily be done), did not gain by soaking in water more than 4th or Toth of a line. 
The second layer (b), at right angles to ره‎ and with its cells parallel to the direction of the 
principal contraction of the valve, consists of a thickened prosenehyma, more collenchy- 
matous in character than that of the innermost layer, c. 4 strip 1 inch in length, 
removed from this layer, after a soaking similar to that to which the strip from layer a 
was subjected, gained about 3% ths of a line, or gth of its length. The third, some- 
what irregular layer (c) consists of parenchyma, the "elis of which are often highly 
coloured. The fourth layer (d) is much interrupted by invasions of the parenchyma of c, 
or by coloured or otherwise altered cells. It is principally composed of a prosenchyma, 
the cells of which are at right angles to those of the contracting layer, 6. A strip 
