581.19 rat 
III 
The Chemistry of the Forest Leaf 
ape fundamental feature of a leaf is, as everybody knows, the 
presence therein of a body called chlorophyll, which is defined 
as “the substance, or maybe a mixture of substances, to which the 
pure green colour of ordinary healthy leaves and of other vegetable 
organs is due.” Here our attention is at once arrested. Is it pos- 
sible that no competent and expert chemist can be found who will 
proclaim with absolute confidence and assurance that chlorophyll is 
a single substance, or that it is a mixture of substances? So far as 
I can find, the original investigator of chlorophyll was Morot, and 
he gave a hypothetical formula for it, but said it was always 
accompanied by a fatty substance which he regarded as the 
chromogen thereof. In 1860 Fremy showed that the green 
matter was a simple mixture of two bodies, viz. a blue (phyllo- 
cyanin) and a yellow (phylloxanthin) existing side by side; 
whereas Pringsheim and others held that these were merely de- 
composition products of an originally single chemical individual. 
On the other hand, Dr Sorby considered the existence of a chloro- 
phyll, a phyllocyanin, or a phylloxanthin of a definite chemical 
composition to be improbable. Meanwhile, an examination of the 
foliar organs of various species among the great vegetable groups 
and classes led Gautier in 1866 and later to conclude that chloro- 
phyll differs among these—nay, even in various species of the same 
genus it may be dissimilar. But the crowning consummation of 
all previous researches seems to have been reached in 1895 when 
Mr Etard, in a memoir read before the French Academy, declared 
that a given species of plant may contain several chlorophylls, e.g. 
he describes four distinct, perfectly defined ones as occurring in 
Lucerne. “It may be concluded,” he states, “that the green 
matters of leaves contain a very stable fundamental nucleus 
carrying the function of optical absorption in connection with a 
biological process; and around this nucleus, this trophic point, 
can be fixed, in a way more or less permanent according to the 
needs of nutrition, different chemical groupings giving place to 
chlorophylls different in their composition, their molecular weight, 
their solubilities, their isomers, and the role which they may play in 
the living species.” “The operations of vegetable synthesis leading at 
the same time to fatty bodies insoluble in water and to matters emin- 
ently soluble, always by the intermedium of absorptive green matters, 
it is natural to think that one and the same chlorophyll would not 
be sufficient for the work” (Comptes Rendus, vol. exx., p. 328). 
N 
