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AMERICAN NATURALIST. 
Vol. VII.—FEBRUARY, 1873.—No. 2. 
CSR OEDOD I> 
COLORS OF VEGETATION.* 
BY PROF. D. S., JORDAN. 
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Tue coloration of plants is due to the presence in the cells of 
minute globules, which are usually green in the herbaceous parts, 
the leaves, sepals, etc., and of various hues in the flowers and 
fruits. 
The normal color of foliage is green, but it may be of almost 
every conceivable shade and degree of intensity. It may be of a 
yellowish-green as in the parsnip, or of a blue-green as in the 
sweet pea. It may be pale and shining as in the orchis, or dark 
and shining as in the laurel.. It may be intense and vivid as in 
the young leaves of the horse-chestnut, or of a neutral Portage 
sandstone color as in the Cassandra or leather leaf. 
The causes of these differences are partly chemical and partly 
physical: the chemical causes producing the different shades of 
color, the physical the differences in brightness and intensity. 
First, as to the chemical differences. The French chemist 
Frémy finds’ that chlorophyl or leaf green is composed of two 
distinct substances: the one of a bright blue color which he 
calls phyllocyanin; the one of a yellow color known as phylloz- 
anthin. The unequal proportions of these two ingredients which 
are simply mixed in the leaf cells would account for the absolute — 
differences in color. Thus in the bluish-green leaves of the pea 
* Read before the Cornell University Natural History Society. 
Entered, according to Act of Congress, in the year 1873, by the PEABODY ACADEMY OF 
SCIENCE, in the Office of the Librarian of Congress at Taupo 
AMER. 
NATURALIST, VOL. VII. 5 (65) 
