264 KRAEMER— NATURE OF COLOR IX PLANTS. [Aprils, 



This yellow principle is combined with plastids, which are about 

 one micron in diameter, being spherical or polygonal in shape, and 

 lying closely packed in the palisade cells of both the upper and 

 lower surfaces of the leaf. The yellow plastids are distinguished 

 from the leucoplastids, which occur in the epidermal and mesophyl 

 cells, as well as the chloroplastids, which are found later in the 

 green leaves, by being smaller, relatively more numerous and by 

 not manufacturing either reserve or assimilation starch. The 

 associated pigment is further distinguished from chlorophyl by not 

 being fluorescent ; in having a broad band extending from 65 to 

 the red end of the spectrum, and another extending from 50-52 to 

 the violet end of the spectrum, when examined by means of the 

 Leitz micro-spectroscope ; and in being less soluble in alcohol and 

 more so in benzin than chlorophyl. This latter characteristic 

 affords a means of partially separating it from chlorophyl, and for 

 this principle I propose the name etiophyl^ and for the associated 

 plastid, which seems to be a distiixt body, I propose a correspond- 

 ing name, etioplast^ these terms being used expressly for the purpose 

 of avoiding confusion. The etioplasts completely pack the cells in 

 which they are found, and may be regarded as meristematic 

 plastids, which later give rise to the chloroplastids. 



The yellow color in certain roots, flowers and fruits is apparently 

 in all cases due to a yellow pigment associated with a plastid 

 known as a chromoplast. These plastids are distinguished from the 

 other plastids by being of variable shape and in usually containing 

 protein grains. The associated pigment resembles in some respects 

 etiophyl and chlorophyl, in that it is more or less soluble in ether, 

 benzol, xylol, carbon disulphide, etc. These pigments, for the most 

 part, appear to be unaffected by either mineral or organic acids, but 

 usually give some shade of green with alkalies, potassium cyanide, 

 sodium phosphate or iron salts. In some cases they are affected by 

 alum, iodine, sodium nitrite, or sodium nitrite and sulphuric acid, 

 as given in Table I.^ 



1 In the examination of plant colors the following reagents were found useful : 

 Sulphuric acid, 10 per cent.; hydrochloric acid, 10 per cent. ; nitric acid, 

 10 per cent.; citric acid, 5 per cent; oxalic acid, 5 per cent.; sodium hydrate, 10 

 per cent.; ammonium hydrate, 10 per cent.; potassium cyanide, i per cent.; 

 sodium phosphate, 5 per cent.; ferric chloride, 3 per cent.; ferrous sulphate, 2.5 

 per cent.; hydrogen peroxide, 3 per cent.; salicylic acid, saturated solution, gallic 

 acid, I per cent; sodium nitrite, i per cent.; sodium nitrite followed by sulphuric 



