758 
GENERAL CONDITIONS OF PLANT-LIFE, 
C. 
H. 
N. 
O. 
Gau tier, 
73"97 
9-80 
4°i5 
10-33 
Hoppe-Seyler. 
73*34 
9*72 
5-68 
9*54 
1-38 
0-34 
Ash 
1*75 
P. 
Mg. 
lOO'OO 
100*00 
From this percentage Gautier deduces the formula Cjg H22 Ng O3, and he points out its 
relation to that of Bilirubin (Gj^ H|g N2 Oo). It is of interest to note that iron was not 
found in either case. The spectrum of Hoppe-Seyler's chlorophyllan is the same as 
that of chlorophyll.] 
Optical Properties of Chlorophyll. If parts of plants that contain chlorophyll are 
repeatedly boiled in water and then quickly dried at a temperature not too high and 
pulverised, a substance is obtained which is easily examined and can be preserved for 
a long time unchanged. From this powder the green colouring matter can be ex- 
tracted by alcohol, ether, or oil. The green solution is speedily changed by the action 
of light in proportion to its intensity, the less refrangible rays of the spectrum acting 
most actively and rapidly. It then assumes a dirty brownish yellow-green colour, the 
green colouring matter having become modified or lost its colour. 
If sunlight that has passed through a stratum of the pure green solution not too 
thick or too dark is decomposed by a prism, an extremely characteristic spectrum is 
obtained in which rays of very various refrangibility appear to have been more strongly 
absorbed the darker the solution or the thicker the stratum. This chlorophyll-spectrum 
has been the subject of much research ; the most recent and comprehensive being that 
of Kraus, from whose description I borrow the following ^ : — 
The spectrum of an unchanged alcoholic solution of chlorophyll shows seven 
absorption-bands, four of which are narrow (Fig. 476 A, I, II, III, IF), and are situated 
in the less refrangible half; while three (F, FI, FII) are broad and are situated in 
the more refrangible half. The latter, distinguishable as distinct bands only in very 
dilute solutions, coalesce, even in the solutions of medium concentration which are 
ordinarily examined, into a single continuous absorption-band occupying the whole of 
the more refrangible half of the spectrum. 
The bands /, //, ///, and IF are situated in the red, orange, yellow, and yellow-green. 
The deep black band /, sharply defined on both sides, lies between Fraunhofer's lines 
B and C ; the three others, shaded off on both sides, diminish in strength in the order of 
their numbers. Between these bands the illumination is dim, and progressively in the 
order of the numbers ; /. e. is less dim between // and /// than between / and //, &c. 
To the left of / the light is undiminished. 
The bands F, FI, and FII in the more refrangible half of the spectrum are shaded 
on both sides; F\s situated to the right of Fraunhofer's Hne F', FI, which is dark in the 
middle, to the left of and on the line G\ T/J may be regarded as the total absorption of 
the violet end. This spectrum has been found in all observations made on the most 
different plants ; Mono- and Dicotyledons, Ferns, Mosses, and Algae. 
The Spectrum of li'ving lea'ves agrees with that of the solution in its main character- 
istics^. The bands I —F are, according to Kraus, easily made out in all ordinary leaves 
^ Kraus, Sitzungsb. der phys.-med. Soc. in Erlangen, June 7 and July 10, 1871. See also 
Askenasy, Bot. Zeit. 1867, p. 225 ; Gerland und Rauwenhoff, Archives neerlandaises, vol. VI, 1871 ; 
and Gerland, Pogg. Ann. 1871, p. 585. [Kraus, Zur Kenntniss der Chlorophyllfarbstoffe u. ihrer 
Verwandten; Stuttgart, 1872. For reference to Mr. Sorby's papers see Sect. 8 a.] 
^ For further evidence of this very remarkable fact see Gerland und Rauvi^enhoff, /. c, p. 604. 
It is not easy to understand how certain physicists can maintain the contrary. [Pringsheim points 
