CHLOROPHTLLINE CHR0MULE8. 115 



The spectrum given by solutions of moderate concenti-ation of 

 chromule shows bands I., II., III., IV., or in some cases I., II., iy.,iii 

 the first or less refrangible half of the spectrum ; in the second and more 

 refrangible half a continuous absorption takes place consisting of bands 

 V.,YI.,Yn., joined, beginning either at F (Trauenhofer), or at varying 

 distances before F, according to the richness of the layer. Layers 

 containing extremely little chromule show only a trace of band I. at 

 first, which becomes more sharply defined on increasing the chloro- 

 phyll matter ; and with a further increase the bands of the second 

 half — v., VI., VII. — appear; after which II. and IV., and finally III., 

 become visible. 



Various conditions may interfere with the above order of appear- 

 ance of these bands, such as : slight chemical changes in the chro- 

 mule ; the influence of more than one solvent ; the varying intensity 

 of transmitted light, &c. Nevertheless it may be taken as a general 

 rule that bands V., VI., VII., in the blue, also bands II. and IV., observe 

 with regard to I. and III. the order of succession as stated above ; and 

 we may consider the invariable predominance of band I. as the charac- 

 teristic mark of all green chlorophyll. It is also the most persistent 

 band of those of the first half. 



It has always been supposed that the 7-banded spectrum here de- 

 scribed belonged exclusively to the green chlorophyll of leaves, and 

 could thus be distinguished from all other chromules, including 

 that of etiolated plants, which latter was believed to have absorptions 

 only in the blue region. Both Askenasy and Kraus held this opinion. 

 A closer examination shows, however, that the chromule of etiolated 

 leaves, which the author proposes to call Etiolin, gives a spectrum 

 nearly identical with that of chlorophyll, only differing as to the 

 amount of absorption in the places corresponding to the chlorophyll 

 bands. This correspondence between etiolin and chlorophyll may be 

 observed by using a m )re concentrated solution of the former. 



The etiolin solutions were obtained from various plants which 

 had germinated in the daik, until the cotyledons had appeared and 

 developed. Even with moderately thick layers, generally before the 

 three bands in the blue have united into a continuous absorption band, 

 the chlorophyll band I. is seen in its right place, very distinctly 

 defined. Further, when the illuminated layers increase in thickness, 

 bands II. and IV. gradually show themselves, and when sufiicienty 

 concentrated, band III also appears. 



It is an important fact that this spectrum of etiolin possesses all 

 the seven bands of the chlorophyll spectrum ; and that bands I., II., 

 III., IV.. lie exactly in the same places as in the case of chlorophyll ; 

 whereas bands V., VI., VII., appear somewhat displaced and nearer 

 to the red. A further difference is, that if the solution be thick 

 enough, band II. invariably appears split. These differences, how- 

 ever, are of minor significance, seeing that similar variations may be 

 produced in any chlorophyll solution under certain definite conditions. 

 "We are thus justified in considering etiolin merely as a slight modifi- 

 cation of chlorophyll produced under different physiological conditions. 

 Etiolin also shows the same red monochromatic fluorescence peculiar 

 to chlorophyll. 



It might, perhaps, be assumed that in etiolated plants there exist 



i2 



