108 
House & Garden 
Live Evergreens For Winter Decorations 
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Charming 
Evergreens from 
Hittlr 
(Free iflarms 
for Porches, 
Windows, Rooms, 
Tables, Window 
Sills, Entrances, 
Sun Parlors, 
Balconies, etc. 
Arborvitae without 
pot 75c each. 
Blue Spruce without pot ^ 
$1.50 each. 
17 Blended Evergreens and Box for $10.00 
Delivered to the Express at Framingham. Mass. 
Plant hardy evergreens in Window Boxes, Pots, Urns and Tubs just 
as you Plant flowers and vines for the warm months. ’ These fragrant 
plants give Holiday cheer to the entire household throughout the long, 
dreary, winter months. 
We ship you the little trees carefully packed in the boxes. You have 
only to remove the cover, fill the box with earth, and plant the trees as 
illustrated in the photograph from which you order. Each box is 3 feet 
long, t inches wide, and about 6 inches deep, painted dark green. The 
only care needed is frequent watering. 
Customers may order the plants without the box, deducting 75c for the box. 
Evergreens in Tots, Urns and Jardinieres are beautiful indoors all win¬ 
ter Eaby Spruces, Pines, Arborvitae, and Junipers are charming on tables 
and window sills. 
Our beautiful large Evergreens are much used in hotels and residences 
as decorations for entrances, sun parlors, balconies, etc. 
10 Arborvitae and Box for $5.00 Delivered to the Express at Framingham, Mass. 
Write for our pamphlet on the uses of live trees for 
indoor decorating. 
Our book of 2-ittle ©rcr Ifarma will help you solve 
your outdoor tree and landscape problems. This 
book sent free on request. 
Htttle HTree Jfanns (Near Boston) 
Nurseries of 
American Forestry Company 
Dept. K-10 15 Beacon St., Boston, Mass. Pine without pot 40c each 
Illllillllllllllllllllllllllllllllllillllll^ 
Chas. W. Meyers 
Ship Models 
Repaired 
SffS ROSES 
are always grov’n on their own roots. 
67 years’ experience. Satisfaction and 
safe arrival guaranteed. Our instruc¬ 
tive book, IHngee “Guide to Rose 
Culture,” describes over 1000 varieties 
of roses and other flowers and how to 
grow them. It’s free. Send today. 
THE DINGEE & CONARD CO. 
Box 1074, West Grove, Pa. 
The SaVo Steel 
ower and Plant Box 
Self-Watering and Sub-Irrigating. For Windows, 
Porches, Sun Parlors, etc. Move Savo Boxes in- 
_■ doors or out and have beautiful Flowers the year 
Patented Jan. 23, 1917. round. 
Leak Proof and Rust Proof 
ALL, YEAH ROUND GARDEN. Perfect AIR circulation and drainage. Aluminum or Dark 
Green enamel finish. Most Efficient. Durable and Artistic Flower and Plant box blade. 
Ask your dealer or write for FREE Booklet. 
SAVO MANUFACTURING CO., Dept. C, 39 So. La Salle St., Chicago, III. 
THE FORMATION of LEAFMOLD 
l rom a?i Address Delivered Before the Washington 
Academy of Sciences 
By FREDERICK V. COVILLE 
W HEN the leaves of a tree fall 
to the ground they begin to de¬ 
cay and ultimately they are dis¬ 
integrated and their substances becomes 
incorporated with the other elements of 
the soil. The same thing happens with 
the leaves, stems, and roots of her¬ 
baceous plants. Such organic matter is 
one of the chief sources of food for 
plants, and its presence in the soil is 
therefore of fundamental importance in 
the maintenance of the vegetative man¬ 
tle of the earth. 
In a series of experiments from 1906 
to 1910 the speaker showed that a con¬ 
dition of acidity is a primary require¬ 
ment of the blueberry ( Vactinium ), 
laurel (Kalmia latijolia), trailing arbutus 
(Epigaea repens), and other plants as¬ 
sociated with them in natural distribu¬ 
tion. Other kinds of plants and plant 
associations require, on the contrary, a 
neutral or alkaline soil. 
It is the purpose of the present ad¬ 
dress to show how the leaves of trees 
in the process of the formation of leaf- 
mold produce at one time or under one 
set of circumstances a condition of soil 
acidity, at another time or under 
other circumstances a condition of al¬ 
kalinity, and after calling attention to 
the acidity of the soil as a fundamental 
factor in plant ecology, to point out 
that a knowledge of certain phenomena 
in the decay of leaves is essential to a 
correct understanding of the distribution 
of vegetation over the earth. 
The Acidity of Oak Leaves 
In the early experiments with blue¬ 
berries it had been found that these 
plants grew successfully in certain acid 
soils composed chiefly of partially rotted 
oak leaves. On the rather natural as¬ 
sumption that the more thorough the 
decomposition of this material the more 
luxuriant would be the growth of the 
blueberry plants, some old oak leaf- 
mold was secured for further experi¬ 
ments. It had been rotting for about 
five years and all evidences of leaf struc¬ 
ture had disappeared. It had become 
a black mellow vegetal mold. 
When blueberry plants were placed 
in mixtures containing this mold they 
did not respond with luxuriant growth. 
On the contrary their leaves turned 
purple and afterward yellowish, their 
growth dwindled to almost nothing, and 
at the end of the season when com¬ 
pared with other blueberry plants grown 
in a soil mixture in which the oak leaf- 
mold was replaced by only partially de¬ 
composed oak leaves the plants in the 
oak leafmold were found to weigh only 
one-fifth as much as the others. This 
astonishing result is exactly contrary to 
the ordinary conception. We have been 
accustomed to believe that the more 
thoroughly decomposed the organic mat¬ 
ter of a soil the more luxuriant its vege¬ 
tation. In this case, however, thorough 
decomposition of the soil was exceed¬ 
ingly injurious to the plants. 
This remarkable difference in effect 
between partially decomposed and thor¬ 
oughly decomposed oik leaves was 
found to be correlated with a difference 
in the chemical reaction of the two 
materials, the partially decomposed oak 
leaves being acid, when tested with phe- 
nolphthalein, and the oak leafmold al¬ 
kaline. 
With rose cuttings and alfalfa seed¬ 
lings in the same two soils exactly op¬ 
posite results followed, those in the oak 
leafmold making a luxuriant growth, 
those in the partially decomposed oak 
leaves showing every sign of starvation. 
Every botanist is familiar with the 
rich woods where trillium, spring beauty 
(Clayto?iia ), mertensia, and bloodroot 
(Sanguinaria canadensis) delight to 
grow, in a black mellow mold made up 
chiefly of rotted leaves. He is familiar, 
too, with the sandy pine and oak woods 
where grow huckleberries ( Gaylussacia ), 
laurel (Kalmia latijolia), princess pine 
(Chimaphda), the pink lady’s slipper 
(Cypripedium accule), and trailing ar¬ 
butus (Epigaea repens). The soil here 
also is made up chiefly of rotting leaves 
and roots. Yet one does not look for 
trilliums in laurel thickets, or for ar¬ 
butus among the bloodroots. Either 
habitat is utterly repugnant to the 
plants of the other. 
Tests of the two habitats show that 
the trillium soil is alkaline, the other 
acid, reactions corresponding exactly to 
those observed in the cultural experi¬ 
ments already described, rose cuttings 
and alfalfa requiring an alkaline soil, 
blueberries an acid soil. The difference 
is as conspicuous in nature as in the 
laboratory and the greenhouse. 
What are the conditions under which 
rotting leaves develop these opposite 
chemical reactions? 
In a ravine in the Arlington National 
Cemetery, near Washington, where the 
autumn leaf fall from an oak grove has 
been dumped year after year for many 
years, every stage in the decomposition 
of oak leaves may be observed, from 
the first softening of the dry brown 
leaf by rain to the black mellow leaf- 
mold in which all traces of leaf struc¬ 
ture have disappeared. When freshly 
fallen the leaves show 0.4 normal acidity. 
Those not familiar with the chemical 
expression “normal acidity” may per¬ 
haps most readily understand the term 
by reference to ordinary lemon juice, 
which has very nearly normal acidity 
in the chemical sense. Fresh oak leaves 
may be conceived therefore as having 
about one-third the acidity of lemon 
juice, gram to cubic centimeter. From 
a soil standpoint smh a degree of acidi¬ 
ty is exceedingly high. Probably no 
tree or flowering plant could live if its 
roots were imbedded in a soil as acid 
as this. A correct appreciation of the 
excessive acidity of freshly fallen leaves 
enables one to understand why it is that 
the leaves of our lawn trees, if allowed 
to lie and leach upon the grass, either 
injure or destroy it. On such neglected 
lawns the turf grows thin and mossy. 
From the height of their initial acidity 
it is a long descending course through 
the various stages of leaf decomposition 
to the point of chemical neutrality, and 
then upward a lesser distance on the 
hill of alkalinity, to the black leafmold. 
Rates of Decomposition 
In order to ascertain the rate of de¬ 
composition in leaves of various kinds, 
observations were begun in the autumn 
of 1Q09 on leaves of silver maple (Acer 
saccharinum), sugar maple (Acer sac- 
charutn), red oak (Quercus rubra), and 
scrub pine (Pinus virginiana), exposed 
to the weather in barrels and in con¬ 
crete pits. In one experiment a mass 
of trodden silver maple leaves 2' in 
depth, with an initial acidity of 0.92 
normal, was reduced in a single year 
to a 3" layer of black mold containing 
only a few fragments of leaf skeletons 
and giving an alkaline reaction. In 
these experiments sugar maple leaves 
have shown a slower rate of decom¬ 
position than those of silver maple, 
while red oak leaves still show an acidi¬ 
ty of 0.010 normal after three years of 
exposure, and leaves of Virginia pine 
an acidity of 0.0SS normal under the 
same conditions. 
The alkalinity of leafmold is due 
chiefly to the lime it contains, the lime 
(Continued on page 110) 
