Apr. is, 1914 
Coloration of Seed Coat of Cowpeas 
39 
uniformly the cells of the palisade layer or is irregularly deposited, we have 
modifications in the color of the seed coat, giving rise to various forms of 
speckling, blotching, marbling, or monochrome coloration. In many 
cowpeas both the alkaline-reacting and the acid-reacting anthocyanin 
are present. As a rule, they are deposited in separate cells, but in a great 
many cases they are to be found in the same cell. When this latter is the 
case, the alkaline-reacting anthocyanin always occupies the lower half or 
third of the cell—that is, the part where the cavity is largest—and is col¬ 
lected in dense granular masses of a deep indigo blue. The rose-colored 
anthocyanin usually occupies the upper portion of the cell or occasionally 
fills more or less the entire cavity. The finding of both alkaline and acid 
reacting anthocyanin in the same cell is in harmony with a well-estab¬ 
lished cytological condition, namely, that one end of a cell may give an 
acid reaction while the other gives an alkaline one. 
That these two phases of anthocyanin pigment are probably the same 
material is easily demonstrated. When thin transverse sections are suf¬ 
fused with neutral distilled water, the rose or purplish anthocyanin 
generally found in the upper end of the cell quickly diffuses into the 
surrounding liquid, thereby rendering more visible any alkaline indigo- 
blue anthocyanin which may occupy the lower portion of the cell. This 
latter, although also soluble in water, is very much slower in dissolving, 
taking several hours to disappear. Moreover, if such sections, instead of 
being treated with distilled water, are treated with a weak alkaline 
solution, such as a 1 per cent solution of caustic potash, both phases of 
anthocyanin undergo the same reactions. The rose-colored anthocyanin 
is immediately changed into an intense blue, and this, together with the 
indigo-blue anthocyanin, slowly passes through different shades of blue, 
green, greenish yellow, pale yellow, and finally is bleached and disappears. 
If, on the other hand, a weak solution of an acid is used, such as a 1 per 
cent solution of hydrochloric acid, both phases of anthocyanin again 
undergo the same reaction. The indigo blue immediately changes to an 
intense rose red and rapidly diffuses in the surrounding liquid. The 
tints assumed by these two phases of anthocyanin pigment are so per¬ 
fectly identical with all the reagents that have been tried that it is 
fair to assume that we have essentially the same material in both cases, 
but in the one instance in an acid state and in the other in an alkaline 
state. 
It will be seen that in all pigmentations of the palisade layer the colors 
are superimposed upon the underlying basal color of melanin-like pig¬ 
ment. It is by means of this palisade layer, therefore, that we secure 
the great diversity in color schemes characteristic of the cowpea. If 
the general pale-buff or orange-brown basal color is modified by even 
deposits of melanin-like pigment in the palisade layer, an intensification 
of the basal color is obtained, which sometimes amounts to a copper 
