1883.] 
AMERICAN AGRICULTURIST. 
181 
nailed under the house, front and back, to 
keep it from the ground, and add materially 
to the comfort of the dog. The movable 
roof, shown raised in the cut, is a great con¬ 
venience in cleaning the house. D. Z. E. 
A Road-Scraper. 
A Road-scraper is shown below, which 
consists of a heavy plank or hewn log, of 
oak or any other hard timber, 6 feet long, 0 
inches in thickness, and 10 inches wide. A 
scantling, b, 2 by 4 inches thick, and 6 feet 
long, and the brace c, are secured to the 
log, a, by a strong bolt. The edge of the 
scraper is made of an old drag-saw, and 
secured by rod-iron nails. The scantling 
serves as a reach, and is attached to the 
front part of a heavy wagon, when in use. 
When the road is very hard, it becomes neces¬ 
sary sometimes for the driver to stand on the 
scraper, to make it take better hold. The 
scraper should be shaped about like d, so 
as to make it run steady, and cause the 
loose dirt to slide to one side, and leave it in 
the middle of the road. 
Chemistry of the Farm and Garden—IV. 
Oxygen is the most abundant element in 
nature. Mixed with nitrogen and other gases 
it makes up one-fifth of the atmosphere. In 
chemical union with hydrogen it forms eight- 
ninths by weight of the water of the globe, 
and combined with various elements it con¬ 
stitutes one-third of all the solid substance of 
the earth. The following table shows the 
composition of 1,000 pounds each of some of 
the common farm crops when perfectly dry : 
Carbon. Hydrogen. 
lbs. 
” lbs.' 
Hay. 
. 45S 
50 
Red clover... 
. 474 
50 
Potatoes. 
440 
58 
Wheat. 
. 461 
58 
Wheat straw 
484 
53 
Oats. 
507 
64 
Oat straw.... 
. 501 
54 
Oxygen. Nitrogen. Ash. 
lbs. 
lbs. lbs. 
387 
15 90 
.378 
21 77 
447 
15 40 
434 
23 
389 
3% 70 
367 
22 40 
390 
4 51 
It is seen that the oxygen is second only to 
carbon. This element, so important in the 
structure of all living things, when in a pure 
and uncombined state is an invisible, odor¬ 
less, tasteless gas, not to be distinguished by 
the senses from common air. Oxygen gas 
is obtained from many of its compounds. The 
common test is to thrust a glowing splinter 
of wood into the mouth of a jar, when, if 
this gas is present, the brand will increase in 
brilliancy and burst into flame. Oxygen is 
the great supporter of combustion, ordinary 
cases of burning being, in fact, the union 
of this gas with some other substance ; the 
rapidity of the burning depends upon the 
quantity of the free oxygen and the amount 
and conditions of the combustible matter 
present. In slow burning—called oxidation, 
like the rusting of iron, etc.—no light or heat 
is observed, but the process differs only in 
degree from the burning of wood, coal, or 
illuminating gas. 
Oxygen gas is introduced into the animal 
system chiefly through the lungs in the 
process of breathing, and thus purifies the 
blood. It is often veiy appropriately called 
vital air, and is the life-sustaining part of the 
atmosphere. Oxygen is supplied to growing 
plants in the form of water, and carbonic acid 
gas, and in combination with many of the 
elements. The free gas is also essential to 
vegetable growth. Its presence has been 
proved requisite to the sprouting of seeds. 
Ingenious experiments show that the pres¬ 
ence of oxygen is necessary for the develop¬ 
ment of stems. The growth of pea vines was 
stopped by coating the young tips with oil 
and chalk to cut off the access of oxygen. 
The same fact is shown by varnishing one 
side of a vine, when it ceases to elongate, 
the unprotected part continuing to grow and 
curve the stem. 
Branches of willow, apple, etc., cut in 
spring time will open their buds under a bell 
jar of pure air, when the oxygen will be 
diminished, while similar buds placed in 
jars of the same kind filled with other than 
oxygen remain unopened. Oxygen gas is 
absorbed by the roots of plants, as is shown 
by excluding this gas from them, when they 
soon die. Flowers require oxygen for their 
development. All these processes, in which 
it has been shown that free oxygen is neces¬ 
sary, seem to depend upon the transfer of 
nourishment from one part of the plant to 
another. Thus in germinating seeds, opening 
flowers, ripening fruits, etc, cases where 
oxygen gas is freely used, there is no increase 
of plant substance, but a change of form and 
place of matter already assimilated. Seeds 
grow at the expense of stored food, starch, 
oil, etc., and the function of the oxygen is to 
aid in effecting the necessary changes until 
the roots are spread in the soil and the leaves 
unfold in the air and sunshine. 
Leaves absorb oxygen as it is needed, but 
during exposure to bright light they exhale 
this gas. This latter is neatly shown by 
placing some fresh leaves in a vessel 
under water and in bright sunlight. Mi¬ 
nute bubbles soon gather on the surface of 
the leaves and accumulate in the neck of the 
funnel, when by removing the cork the tests 
for oxygen gas may be made with success. 
It has been stated in an earlier article that 
the carbon of plants is taken from the atmos¬ 
phere as carbonic acid gas, and the oxygen of 
this compound is returned to the air while 
the carbon is retained. 
The supply of oxygen for the growth of 
plants is ample, and the farmer and gardener 
do not have to consider this important ele¬ 
ment in the light of a needed fertilizer. 
The “Potato Rot.” 
One of the most destructive diseases of 
cultivated plants is the “wet rot” in pota¬ 
toes. This trouble was very extensive in 
1842, and again in 1845, when it spread over 
Great Britain, Ireland and the United States, 
causing great suffering to those who rely 
largely upon the potato as an article of daily 
food. The “ rot ” is due to the growth of a 
microscopic fungus (Peronospora infestans) 
that infests the potato plant in all its parts. 
This destructive parasite is closely related to 
the grape mildew fungus, so familiar in many 
American vineyards. The fungus makes its 
appearance in frost-like patches upon the 
under side of the potato leaves, soon causing 
the foliage to curl, turn brown and die. The 
stems are next attacked, and through them 
the disease passes down to the tubers, where 
the destructive work is completed. 
The “ rot ” plant consists of a multitude of 
minute threads that run in all directions 
through the substance of the potato plant. 
These fine filaments rob the surrounding 
tissue of its nourishment, and induce a rapid 
decay. The engraving shows a small portion 
of the under surface of a diseased potato 
leaf, much magnified, with the fungus 
threads in the leaf, and extending from the 
stomata or breathing pores. The filaments 
pass out of these openings, and branching, 
bear the spores as small oval bodies on the 
tips. These spores, with the fine branches, 
make up the frost-like patches on the surface 
of the affected leaves. 
The “ rot ” usually appears in midsummer, 
and is associated with rain—“muggy” 
weather being favorable for its development. 
Early and quick-growing varieties of potatoes 
are recommended when practicable, as they 
are much more likely to be ripe before the 
pest makes its appearance. Much has been 
said about ‘ 1 rot-proof ” sorts, but knowing 
that the disease is caused by the fungus, the 
development of which is favored by moist, 
HIGHLY MAGNIFIED VIEW OF POTATO ROT. 
warm weather, and hindered by the opposite, 
there is little hope of finding a kind that will 
differ so much from others as to be disease- 
proof. In England prizes have been offered 
to encourage the work of finding out the 
sorts of potatoes best able to withstand the 
attacks of the fungus, and elaborate experi¬ 
ments have been carried out without any 
satisfactory positive results. 
The farmer should be on the watch for the 
appearance of the disease, and harvest the 
crop as soon as possible after the trouble is 
found in the field. This may prevent the 
fungus from reaching the tubers. After 
digging, the potatoes should be placed in a 
dry and cool place, thus providing the most 
unfavorable conditions for the development 
of the disease. As a precaution against the 
propagation of the fungus, it is well to gather 
and burn all the old vines after digging, thus 
destroying the multitudes of spores that may 
have formed. Any tubers that are affected 
should be thrown out, and either fed to stock 
or burned. One diseased potato may com¬ 
municate the “ rot” to a whole heap or bin. 
