1872.] 
AMERICAN AGRICULTURIST. 
423 
cavities of microscopic size, roundish or long, 
according to the part of the plant in which they 
may be. A cross-cut of either the leaf, stem, or 
tuber would appear under the microscope much 
like a honeycomb, it being, like that, made up of 
cells. This being in brief the structure of the 
plant infested, let us consider the fungus. The 
potato-rot fungus is a minute, microscopic 
plant, but a plant for all that as much as the 
potato itself is. We are familiar enough with 
the larger fungi, the mushrooms and toadstools, 
which show on a large scale much the same 
manner of growth as the small fungi. When a 
gardener wishes to raise mushrooms he puts 
some spawn in a bed of manure. Soon the 
spawn begins " to run," and the manure is filled 
with whitish cobwebby threads, visible to the 
naked eye. After some weeks, mushrooms ap- 
pear above the surface of the bed. To compare 
the vegetation of the mushroom with our com- 
mon plants, the white threads of the spawn 
(mycelium of the botanists) may be compared to, 
as they serve the purpose of, the roots, stem, 
and needs no leaves, while the smallest portion 
of it will go on and grow and rapidly multiply, 
and the fungus is propagated in this way just 
as we multiply a plant of a higher order by 
cutting of the root or stem. The rust, blight, or 
rot, as it appears above the surface of the stem 
or leaf, is, when examined by the microscope, a 
collection of club-shaped threads (fig. 1), which 
ultimately produce an exceedingly minute dust 
or spores (fig. 2), which in the fungus answer the 
purpose of seeds. These spores are so small that 
they can be carried about in the air, or be trans- 
ported unobserved while lodged on other bodies. 
From what has been said, it will be seen that in 
the potato-rot fungus we have to deal with an 
exceedingly subtle enemy. It can, in the first 
place, work great damage inside of the tissues 
of the plant before its ravages are apparent, and 
it is propagated by spores or dust so minute 
as to escape detection. This being a brief his- 
tory of the fungus, which science has made out 
in much greater detail, it will be asked, What 
remedy has science to offer? We are sorry to 
FIG. 2 
the fungus of the potato-rot.— Peronospora infestam.) 
Fig. 1. Tlie fungus as it appears on stems (a) and leaves (/•>. Fig. 1. Spores in different states. Fig. 3. Zoospores. 
The two figures at tlie right, marked b and c, show the mycelium penetrating the cells of Vie plant. 
and leaves of ordinary plants, and the mush- 
rooms, which alone appear above the surface of 
the bed, represent flowers and fruit. The mush- 
rooms only appear when the mycelium or spawn 
Which is running and branching in the manure 
attains sufficient strength to reproduce itself by 
means of the above-ground portion. Now, the 
potato fungus has a similar manner of growth, 
but its mycelium or spawn, instead of reveling 
in a bed of manure, finds its home iu the sub- 
Stance of the plant. It lives in the cells already 
mentioned, and runs from one to the other, be- 
ing nourished by their contents and substance. 
After a while, the mycelium having become 
sufficiently strong, it throws up reproductive 
organs, corresponding to, though unlike in ap- 
pearance to, mushrooms, and this is the visible 
mold or rot that is seen in the stem and leaf 
of the potato. The fungus has two ways of 
propagating. First, by the mycelium or spawn, 
which branches and spreads in the tissues 
of the potato, just as the root of quack-grass or 
Canada thistle will spread through the soil. It 
lives on the already prepared food in the plant, 
be obliged to reply, None. Some varieties are 
less liable to attack than others, and it is grati- 
fying to know that our American varieties, 
notably thosp raised by Mr. Goodrich and their 
descendants, are especially exempt. It would 
be well that the importation of foreign seed- 
potatoes were stopped. At all events, we ad- 
vise no one to plant an English potato as long 
as the present trouble continues. Secondly, 
should the disease break out on any farm, no 
potatoes should he sent out from it under any 
circumstances. This will not absolute])' pre- 
vent the disease from spreading, but will do 
much to prevent it. 
The IlAiiDiNESs of Tropical Seeds. — 
Some of the tropical plants of our gardens 
arc killed by the slightest frost, and one would 
suppose that their seeds would have their 
vitality destroyed by the cold of our winters. 
That such is not the case is shown by the 
Tomato, as it is a matter of common observation 
that this comes readily from self-sown seeds. 
This season we devoted a bed that was last year 
occupied by Cannas to other plants, and were 
much annoyed by the appearance of an abun- 
dance of seedling Cannas. Job's Tears {Vow 
Lachryma), a very tender tropical grass, has be- 
come almost a weed with us. So with the 
ornamental Amaranths; they make themselves 
at home, and we should not be surprised to find 
that in a few years the now rare Amarantu* 
salicifolius had become a common weed. 
Preserving Roots. 
■ 
Market-gardeners and those who have a con- 
siderable quantity of vegetable roots to keep 
for winter use will of course pack them i» 
trenches, but the family supply is usually kept 
in the cellar. When put loosely into bins and 
barrels, the roots, if the cellar be a dry one, be- 
come shriveled and injured before spring. 
This difficulty is avoided by packing in dry 
sandy earth — the sandier the better. We scrape 
off a cart-load of soil from a piece that has bee« 
recently harrowed, and use this for the roots. 
Beets, carrots, salsif}', parsnips, horseradish, 
etc., are laid in boxes or barrels, as may be 
most convenient, with plenty of earth distri- 
buted among them. In this manner the root* 
are preserved perfectly fresh, and should any 
chance to decay, which is rarely the case, all 
odors are prevented from escaping by the earth. 
Flower-roots, such as dahlias, caladiums, and 
cannas, may be successfully preserved by th» 
use of earth, which for them may be quite dry. 
These tropical roots not only need to be kept 
dry, but warm, and if the cellar is a damp one 
they can hardly be preserved. A spare closet 
in a part of the house where there is no danger 
of freezing is preferable to a cellar for these. 
Thawing and Freezing of Cold-Frames. 
BY PETER HENDERSON. 
A. Leavens & Co. ask the question, " How- 
much freezing and thawing plants of lettuce, 
cabbages, etc., will stand without being de- 
stroyed?" In former articles I have taken the 
ground that the thawing, instead of being inju- 
rious, is a necessity for their safety. In doiug 
so I know I run in direct opposition to a 
large majority of my brethren, but the expe- 
rience of nearly a quarter of a century, yearly 
increasing in extent, confirms me that I am cor- 
rect, and I am further assured in my opinion 
by knowing that there is not a market-gardener 
in this vicinity but whose practice in the man- 
agement of cold-frames is the same as my own, 
though if the question was asked some of 
them if thawing and freezing did not injure 
plants, the answer might lie in the affirmative, 
so universally has the dogma been accepted. 
The gentlemen also ask: "How long can 
frozen plants be kept from the light under shut- 
ters?" — Much would depend on atmospheric 
conditions. If the temperature ranged at night 
from 25* to 32' — merely sufficient to mildly 
freeze the plants — they might remain in good 
condition for four or five weeks, but if subjected 
to a zero atmosphere, without change, as manv 
days might prove injurious. A very common 
practice with cold-frames in this vicinity is, if 
the plants are frozen in tlie frames previous t» 
a snow-storm, we allow them to be covered up 
by tlie snow often for two or three weeks, pro- 
vided that it is deep enough to protect th« 
plants from severe frost?, as iu that condition 
the plants, though excluded from light, are sub- 
jected only to a temperature of from probably 
