234 Schunck . — The Chemistry 
such as zinc and hydrochloric acid, a product which he 
names ‘ protophyllin,’ and from which, according to him, 
chlorophyll may be reproduced by oxidation. It is contained, 
he says, in etiolated plants, from which it may be obtained 
by extraction with alcohol, the extracts showing no trace 
of the chlorophyll-band I, whereas band II is relatively dark 
and well defined. When kept in the dark and in an 
atmosphere of carbonic acid, the solution retains its yellow 
colour, but on exposure to light it turns green. Hence it has 
been inferred that the author considered the necessary oxy- 
gen to have been obtained by decomposition of the carbonic 
acid : but he does not, he says, go so far as this, it being 
possible there were traces of oxygen present in his solutions, 
which only acted on exposure to light. The author’s re- 
searches have led him to conclude that the turning green 
( verdissement ) of etiolated plants is due to the action of 
light, and that it is the rays absorbed by the chlorophyll 
that effect the decomposition of carbonic acid in plants. 
I confess that I am at a loss to understand the reactions 
described by M. Timiriazeff. By the action of hydrochloric 
acid, chlorophyll is decomposed, yielding phyllocyanin and 
phylloxanthin, and these by the further action of zinc and 
hydrochloric acid give red products which cannot be recon- 
verted into chorophyll by oxidation, and though I have 
never made a special study of etiolin, the yellow colouring- 
matter of etiolated plants, I have never found any reason 
to suppose that it is converted into chlorophyll with or 
without the concurrence of light, the products of its oxidation 
being always colourless. The same author 1 shows by an 
ingenious experiment that it is the rays of light absorbed 
by the chlorophyll which chiefly promote the formation of 
starch in leaves. A plant having been kept in the dark 
for two or three days so as to allow all the starch contained 
in the chlorophyll-corpuscles to be absorbed, the image of 
a well-defined spectrum is thrown on one of the leaves 
contained in a dark chamber by means of a heliostat, an 
1 Comptes Rendus, cx. 1346. 
