674 
Journal of Agricultural Research 
Vol. XI, No. 13 
from 300 to 1,500 fi. The surface of the hairs is roughened with minute 
tubercles, increasingly so toward the apex. The smaller hairs are color¬ 
less, and on account of a relatively thicker wall remain cylindric, while 
the larger ones collapse and become blackish and twisted. 
Carpeixary wale (PI. 50, C, G).—The wall of the pod consists of an 
outer layer of epidermal cells, polyhedral in form, 15 to 30 m thick, 
approximately cubical, and 15 to 30 /* in diameter. They are filled with 
dense protoplasm. The numerous basal cells of the hairs are conspicuous 
on account of the black base of the hairs. Stomata of typical form are 
about one-half as numerous as the hair bases. 
Beneath the epidermis lie about five layers of peculiar sclerenchyma 
cells (PL 50, G, H, I, J) from 50 to 234 ju in length. The cells are spindle- 
shaped, and two to six times as long as broad, the lumen broadening at 
each end. 
The inner half of the pod consists of small-celled parenchyma and 
numerous longitudinal bundles of thick-walled fibers (PI. 50, D, E, E, G), 
300 to 500 n long. The lumen of these fibers is small, and in section 
numerous lateral extensions are apparent. 
The innermost layer of the pod is satinlike and consists of thin-walled 
parenchyma (PI. 50, A). 
The fibrovascular bundles which traverse the pod require no particular 
mention. Their structure in cross section is illustrated in Plate 50, B. 
STRUCTURE OF THE SEED 
The most characteristic external feature of the seed of the velvet bean 
is the thick, white caruncle which surrounds the hilum (PL 51, A): 
In cross section (Pl. 51, B) this is seen to be composed of thick-walled 
parenchyma. 
Testa. —In cross section (PL 51, B, E) the testa is seen to be composed 
of an outer layer of long palisade cells, a second layer of the so-called 
“hour-glass” cells, the central portion of nearly empty parenchyma, and, 
between this and the small-celled inner epidermis, several layers of paren¬ 
chyma filled with protein. 
The palisade cells (PL 51, C, D) are thick-walled cylinders, 100 to 180 jj, 
long and 10 to 22 fx in diameter. In the neighborhood of the hilum the 
palisade cells are longest and broken near the middle by the so-called 
“light line,” owing to the fact that these cells have the lumen much 
enlarged near the middle. 
The hour-glass cells (Pl. 51, F, G) are 50 to 100 ju long. They closely 
resemble those of related genera (Phaseolus, Vigna, Soja). 
The cotyledons (PL 51, I, J) consist mainly of an outer epidermis of 
polyhedral cells about 10 jw in diameter; an inner epidermis of cells more 
than twice as large; and between, the much larger cells of the body of 
the cotyledons. All the cells are filled with grains of starch and proteids. 
The starch grains show no special peculiarities. 
