Apr. is. 19x4 
Coloration of Seed Coat of Cowpeas 
55 
fourth, there are occasional spots in the form of large roundish intensely 
black areas. Transverse sections show that the general structure of the 
seed coat is identical with that of cultivated varieties. The palisade 
cells are of the same general shape and are as to size in the usual propor¬ 
tion to the rest of the seed coat. The underlying layer of so-called hour¬ 
glass cells is also the same and is, as elsewhere, empty. Beneath this is 
the usual basal-color layer, supplied with the regular orange or yellow 
melanin-like pigment. The red areas of the seed coat overlying the basal 
clay or buff owe their color to a strong orange or red-brown pigment in 
the palisade cells, identical in organization and in its reactions with the 
similar color in cultivated varieties; in other words, a melanin-like pig¬ 
ment. The fine speckling is in this case also due to an intense blue 
anthocyanin pigment in the lower end of certain palisade cells and it is 
also here associated with the melanin-like pigment mentioned under former 
headings, and, as in the other cases, it responds very slowly to the reac¬ 
tion of reagents. Furthermore, the areas represented in the seed coat by 
large black spots contain both red acid anthocyanin and blue alkaline 
anthocyanin, as is the case in the black areas of cultivated cowpeas. 
The complete uniformity of methods of coloration, as well as of schemes 
or patterns of coloration in this supposedly wild cowpea, when compared 
to our cultivated varieties, is of considerable interest. There is no trace 
of distortion or irregularity in the palisade layer. Of course, no knowl¬ 
edge is obtainable as to its origin. It was received from Kew Herbarium . 
and was collected by J. M. Dalziel. 
SUMMARY 
The greatly diversified color schemes of the different varieties of cow¬ 
peas may therefore be reduced to two factors: (1) An extremely uniform 
basal color, ranging from very pale yellow to deep copper red, but found 
to be in all cases due to a melanin-like pigment deposited in the basal-color 
layer, the differences in tint being unquestionably caused by differences 
in quantity rather than in character of the pigment present; and (2) a 
superimposition upon this basal color of variously arranged pigment areas 
in the palisade layer, the outer layer of the seed coat, the pigments here 
being of only two kinds, first, a melanin-like pigment very generally iden¬ 
tical in color and behavior to that found in the basal layer, and, second, an 
anthocyanin pigment, either associated with this or found in separate 
cells. And further, this anthocyanin pigment may be of a red color, on 
account of an acid condition, thereby producing various shades of purple 
and rose; or it may be alkaline in character, thereby producing various 
shades of blue and black, and these two may be found in the same cells 
or in some instances in separate cells. Finally, according as only one, or 
more than one, or all of these pigments sometimes found in the palisade 
layer are actually present there, and according as they are uniformly dis¬ 
tributed throughout its cells or are variously localized in large or small 
