134 MISSOURI BOTANICAL GARDEN BULLETIN 
maturity which may lead toward death. In general, the 
autumn colors may be classed as yellows and reds, although 
orange, brown, bronze, and purple may be found in the 
varied effects. The yellow and orange tints are due pri- 
marily to a group of pigments called xanthophyll, in reality, 
xanthophylls and carotins, while the reds are almost invar- 
iably anthocyanin. These names mean little more than the 
colors themselves until one discovers that there are extensive 
groups of plant pigments which have merited careful chem- 
ical and phitiskadent study and classification. 
Even the green leaves of the summer season exhibit some- 
times a shade of yellow, and with a host of plants yellowing 
is associated with waning vigor and health. As a matter of 
fact, yellows are always present in the leaves, associated with 
the chlorophyll, or leaf green, so that when the conditions 
become unfavorable for the maintenance of health, the 
chlorophyll is broken down and the yellow pigments (in 
those plants which do not produce reds) become more con- 
spicuous. These yellow pigments, like the chlorophyll, are 
not sap colors; moreover, they are more stable than the green, 
and may persist until the living cells are killed by cold. 
One of these yellow pigments, carotin, is also characteristic 
of many fruits, of certain mushrooms, and it is even found 
in various animal tissues. 
In the vicinity of St. Louis yellow is the autumn color of 
the ginkgo among conifers, likewise of many species of wil- 
low Ne sa birch, and certain maples, also of box elder, mul- 
berry, elm, hornbeam, chestnut, tupelo, and sycamore. It ap- 
pears as an undertone where browns and reds are more prom- 
Inent, as in the sassafras and horse-chestnut. The yellows 
in some foliage plants conspicuous in the summer season, 
as in certain varieties of coleus, are simply indicative of a 
preponderance of yellow pigment, veiling shi leaf green but 
not excluding it. 
The red pigments of autumn leaves are cell-sap colors, and 
nearly all such anthocyanins are soluble in the aqueous solu- 
tion constituting the plant juices. It is significant that those 
plants exhibiting conspicuous red coloration in the autumn 
are often those which give indication of reddening with the 
first shoots of the spring growth. In this region fakes is no 
plant more loyal to autumn scarlet than the sumac, and in 
the spring the young shoots are reddened until the vigorous 
growth of warmer weather disperses the tint. Instances of 
this sort might be multiplied many fold. 
In our own flora some species exhibiting pronounced reds 
are hard maple, sassafras, thorn-apples, sumac, dogwood, 
