21 
“ 
the others; the cells are more or less elongated laterally, that 
is, in the direction of the seed-coat. The cell walls are greatly 
thickened and are beautifully pitted. The cell cavity is very 
narrow, and often hasan irregular outline with peculiar markings. 
The cells of this layer change somewhat in size and shape as 
they are followed inwardly, becoming more like the parenchyma 
of the fifth layer. The fourth is a very narrow layer and carries a 
brownish-yellow pigment. This is followed by the fifth layer, 
which is made up of a comparatively thick-walled parenchyma ; 
well-developed spiral vessels are also found in it. 
The sixth layer may be divided into two parts. In the first 
the intercellular spaces are small, while in the second they are 
large and numerous. The first part (/) is made up of thick-walled, 
star-shaped cells, which have an irregular outline (Fig. 11). The 
cell walls are thickened irregularly, as shown in the figure. There 
are from one to four pits in a cell wall; sometimes these pits are 
small and narrow (Fig. 11., 6). A number of oil globules are usually 
distributed through the protoplasm of each cell. The cells of 
the second portion (g) of the sixth layer are star-shaped in a tan- — 
gential section, and have the same peculiar pitted walls as those 
of f. The cell walls of one kind of these cells are thinner 
than those of £ while the cells of a second kind have as thick 
walls as those of a, Fig. 11. The protoplasm is very granular 
and has oil globules distributed through it. 
THE CALABAR BEAN (Physostigma venenosum, Balf.)—There 
is a marked difference between the seed-coats of Gymnocladus and 
those of the calabar bean. The former, when soaked in water, 
become mucilaginous and fragile, whereas the seed-coats of the _ 
latter are coriaceous and somewhat flexible and have some affin- — 
ities with those of the sea bean. 
In a surface view the palisade cells are five or six sided aid 
very often elongated (Fig. 13). The folds are often branched 
equilaterally, as in Fig. 12, or are of an abnormal form, as shown i in 
Fig. 13. A peculiar feature of these palisade cells, macerated in 
concentrated potash, is that they show numerous intersecting stri- 
ations (Figs. 14 and 15) running obliquely, or almost horizontally, 
