October, 1918 
WISCONSIN HORTICULTURE 
15 
continue making roots if unhin- 
dered by frost. 
Hyacinths are better adapted 
to indoor gardening; unless it be 
in public parks or large estate 
plantings, we seldom find them in 
the cottage gardens. They are 
considerably more expensive. Out 
of door culture is the same as with 
Tulips, only they must be covered 
with leaves or straw, as they are 
less hardy. Some of the best sin- 
gle varieties are : Gertrude, rose 
pink, Moreno, pink, La Grandesse, 
white, Mine. Vander Hoop, white, 
Czar Peter, light blue, Grand 
Maitre, sky blue, King of the 
Blues, dark blue. 
Why the Leaves Change Their 
Color. 
it requires no vivid imagina- 
tion to picture Mother Nature go- 
ing about these days with a liber- 
al supply of paint with which she 
colors the leaves of the trees and 
other plants and thereby pro- 
duces the vivid tints which char- 
acterize the foliage of this season. 
In reality the change of coloring 
is the result of certain chemical 
processes which take place in the 
leaves. 
The change is not, as many peo- 
ple suppose, due to the action of 
frost, but is a preparation for win- 
ter. All during the spring and 
summer the leaves have served as 
factories, where the foods neces- 
sary for the trees’ growth have 
been manufactured. This food 
making takes place in numberless 
tiny cells of the leaf and is carried 
on by small green bodies which 
give the leaf its color. These 
chlorophyll bodies, as they are 
known, make the food of the tree 
by combining carbon taken from 
the carbonic acid gas of the air 
with hydrogen, oxygen, and vari- 
ous minerals supplied by the wa- 
ter which the roots gather, in 
the fall when the cool weather 
causes a slowing down of the vi- 
tal processes the work of the 
leaves comes to an end. The ma- 
chinery of the leaf factory is dis- 
mantled, so to speak, the chloro- 
phyll is broken up into various 
substances of which it is composed 
and whatever food there is on 
hand is sent to the body of the 
tree to be stored up for use in the 
spring. All that remains in the 
cell cavities of the leaf is a watery 
substance in which a few oil glob- 
ules and crystals, and a small 
number of yellow, strongly re- 
fractive bodies can be seen. 
These give the leaves the yellow 
coloring so familiar in autumnal 
foliage. 
It. often happens, however, that 
there is more sugar in the leaf 
than can be readily transferred 
back to the tree. When this is 
the case the chemical combination 
with the other substances pro- 
duces many colored tints varying 
from the brilliant red of the dog- 
wood to the more austere red- 
browns of the oak. In coniferous 
trees, which do not lose their foli- 
age in the fall, the green coloring 
matter takes on a slightly brown- 
ish tinge, which, however, gives 
way to the lighter color in the 
spring. 
While the color of the leaf is 
changing, other preparations are 
being made. At the point where 
the stem of the leaf is attached to 
the tree, a special layer of cells 
develops which gradually sever 
the tissues which support the leaf. 
At the same time Nature heals the 
cut, so that when the leaf is final- 
ly blown off by the wind or falls 
from its own weight the place 
where it grew on the twig is 
marked by a scar. 
Although the food which has 
been prepared in the cell cavities 
is sent hack to the tree, the min- 
eral substances with which the 
walls of the cells have become im- 
pregnated during the summer 
months are retained. Accordingly 
when the leaves fall they contain 
relatively large amounts of valu- 
able elements, such as nitrogen, 
and phosphorus which were orig- 
inally a part of the soil. The de- 
composition of the leaves results 
in enriching the top layers of the 
soil by returning these elements 
and by the accumulation of humus 
That is why the mellow black 
earth from the forest floor is so 
fertile. But if fires are allowed to 
run through the forest and the 
leaves are burned, the most valu- 
able of the fertilizing elements 
are changed by heat into gases 
and escape into the air. As a re- 
sult, forests which are burned 
over regularly lose their soil fer- 
tility even if no apparent damage 
is done to the standing timber. — 
U. S. Dept, of Agriculture. 
Hydrangea Paniculata flowers 
cut before they are frosted will 
last well into the winter if put into 
a dry vase. 
Clean up the garden as early as 
possible and plow or spade it this 
fall. Many insects will be de- 
stroyed by doing this. 
As soon as the frost has killed 
the asparagus foliage, it may be 
cut off and burned. Young plants 
may be started by saving and 
planting the seeds when ripe. 
