23 
20; others straight and longer, as in Fig. 19. Though small, 
the folds are well defined. The same clear definition was also 
obtained in a surface view of the palisade cells. In none of 
the specimens studied could the outlines of the cell walls, their 
cavities, or of the folds be made out as in this species. The 
palisade cells show a slight indication of the characteristic stria- 
tions of those of the calabar bean. 
The second layer (Fig. 18, II) may be divided into two parts. 
The first of these is a single layer of cells homologous with the 
crystal layer of Phaseolus and the I-shaped layer of Gymmnocladus 
and Physostigma.* But according to A. Sempolowski (1. c., pp. 28, 
30), the second layer is not identical in its structure with the layers 
which follow, but has the true support-cells. There are certainly 
gradations from true support-cells to the parenchyma which fol- 
lows in many of the Leguminose. (G. Beck and others.) 
The cells of this layer differ from those that follow in that 
they are much thicker walled and have a small cell cavity. They 
are separated by narrow and large intercellular spaces. The 
fibro-vascular elements are present in the lower portion of this 
layer. 
These are the chief characteristics of the seed-coats under 
consideration. From the account which has been given, it will 
be seen that the hard-walled leguminous seeds do not differ 
much in the nature and arrangement of their protecting envelopes 
from those of a less resistant character, their greater firmness _ 
depending usually upon the greater development of one or 
more of the layers which are normally present, and upon differ- 
ences in the nature of the walls of their component cells. The 
microchemical behavior of the walls in the several cases, and es- 
pecially certain interesting peculiarities of the refractive portions _ 
constituting the so-called light lines, must, however, be reserved 
for consideration in another place. 
*According to Nobbe, Samenkunde, p. 79, the cells between the palisade layer 
and aleurone layer of Trifolium pratense, and Medicago sativa are identical in structure, 
excepting the fibro-vascular elements carried in the lower portion of the layer. 
Giinther Beck (l.c., p. 547). speaks of the ‘‘ Hartschichte” and the ‘Quell- 
schichte ” ; in the latter he places (1) the I-shaped support-cells, (2) the true — 4 
tissue, (3) the fibro-vascular elements and their surrounding tissue. EE: 
