I20 BOTANICAL GAZETTE [FEBRUARY 
He showed that etiolated wheat seedlings contained 8-10 parts 
of carotin to one of xanthophyll, and that leaves of Hordeum 
murinum when kept in darkness turned yellow or yellowish red. 
When analyzed for plant pigments, the leaves were found to contain 
chlorophyll, xanthophyll, and carotin in the proportions 1, 3, 
and 12, respectively, and in addition a red pigment, which was 
apparently a flavone, believed to be a decomposition product of 
chlorophyll. His suggested explanation of the greening of etiolated 
plants is unique. When an etiolated plant turns green in light, 
the carotin undergoes photo-oxidation. The bleached carotin 
residue combines with glaucophyllin, converting it into the tri- 
carboxylic chlorophyll. 
WILIsTATTER found that a weak alcoholic oxalic acid solution 
splits (in the cold) magnesium out of the chlorophyll molecule. 
On this basis Swart assumes that the decomposition of chlorophyll 
in yellowing leaves is due to acids, thus splitting the chlorophyll 
molecule. This postulates an increase of acidity with yellowing, a 
theory for which there is no evidence. SAMPSON (43), in testing the 
acidity of Coleus leaves, found that fresh yellow leaves in the act 
of abscissing had an acidity equivalent to o.oo69 cc. of N acid 
per gram of wet weight, while fresh green leaves had an acidity 
equivalent to 0.0089 cc. of N acid. Since the green leaves are 
more acid (at least as measured by their base absorbing power) 
than the yellow ones, if Swart’s assumption is correct, one would 
expect to see the top leaves of the plant yellow instead of green. 
It is hardly probable that the splitting of magnesium out of the 
chlorophyll molecule, due to acid accumulation, is the first step in 
chlorophyll decomposition. PALLADIN (40) pointed out that 
carbohydrates are essential to the formation of chlorophyll. From 
the sand culture experiments with Coleus one could hardly say 
that the deficiency in carbohydrates caused the chlorophyll to 
disappear. It would be more accurate to say that the carbohy- 
drate output was decreased, owing to the deficiency in chlorophyll. 
WIESNER (52) supposed that the chlorophyll in the living leaf 
was dissolved in an oil, in which the concentration of chlorophyll 
was very high and the decomposition very low. IwANowskKI (21) 
agreed with WIESNER in regard to the concentration of the chloro- 
