294 proceedings: botanical society 



Distribution of pigment in the seed-coat of the cowpea: Albert Mann. 

 The question of the arrangement of pigments in the seed-coat of 

 the cowpea was studied because of the bearing of certain phenomena 

 upon questions of heredity now being studied by Prof. W. J. Spillman. 

 Transverse sections of the seed-coat disclose three principal layers of 

 cells, the outer one being a palisade layer with long axis vertical to the 

 surface and with the cell cavit} r club-shaped and having the larger end 

 at the lower extremity of the cell, the upper end of the cavity being 

 often reduced to a mere thread. Second, a heavy-walled layer below 

 this of empty cells; and third, a layer of considerably compressed cells 

 with long axis parallel to the surface of the cowpea. 



It was found that the colorations in the cowpea are the result of pig- 

 ments deposited in two of these layers. In all colored cowpeas there 

 is a basal color or practically uniform tint and invariably to be found 

 in the lowest of the three layers, to which is therefore given the name 

 of the basal color layer. This is a melanin compound and is of an orange- 

 yellow tint, grading into lemon-yellow and pale buff. The changes in 

 intensity are probably not due to a difference in the character of the 

 pigment, but to a difference in the quantity. All other colors are 

 obtained by superposing upon this basal color layer various pigments, 

 and these are uniformly deposited in the palisade cells, and as a rule 

 in the lower and larger third of the cell cavity. The colors to be found 

 here are of practically three kinds: first, a black to blue-black, or some- 

 times purple tint which is an anthocyanin. Secondly a yellow or brassy- 

 brown pigment which is some melanin compound; and third,_ an intense 

 black pigment which is also a melanin compound. By various arrange- 

 ments of these three superposed tints in the palisade cells, or by the 

 absence of any pigments in these cells, the various schemes of coloration 

 in the cowpea are obtained; the marbling, blotching, dotting, as well 

 as the uniform colors of some cowpeas being produced by the basal 

 color plus such superposed arrangements of color in the palisade cells 

 as are characteristic of the different varieties. 



In the case of the few cowpeas having white or colorless seed-coats, 

 the result is obtained by the suppression of all pigments both in the 

 basal color layer and in the palisade layer. 



A wild cowpea secured from North Nigeria, Africa, is of particular 

 interest, in that upon the same cowpea all the elements of color, as well 

 as all the schemes of coloration are to be found. This cowpea, which 

 is from one-seventh to one-eighth the size of the average cultivated 

 cowpea, has a seed-coaj that morphologically is identical in structure 

 with that of cultivated cowpeas; the methods of pigment deposit are 

 found to be also identical with those seen in the cultivated varieties. 



The purpling chromogen of the Hawaiian bitter yam: H. H. Bartlett. 



Illustrations of the phytog'eography of the North American Continent: 

 John W. Harshberger (by invitation). The speaker displayed to 

 the Society an album of twelve volumes of photographs and illustrations 

 of North American vegetation collected during the preparation of his 

 recently published work on the phytogeography of North America. The 



