1875.] 
AMERICAN AGRICULTURIST. 
263 
mate host in the present case, and that the potato- 
rot may be propagated by means of oOspores which 
hibernate in this and other fodder-plants, and which 
reach the potatoes by way of the animal manure. 
At present this is a mere suspicion, one which sug¬ 
gests investigation. But the recent announcement 
that it is now known to be so, through the discover¬ 
ies of Professor De Barry, is pronounced to be 
wholly unfounded. It does seem, however, that, 
in England, “there is a tendency for the rot to 
prove particularly bad when potatoes follow clo¬ 
ver.”—So that it is worth while to follow up the 
clue, both by investigation and observation. In 
order that farmers may do their part of the latter, 
Prof. Farlow propounds to them the following 
questions for this year’s consideration : 
1. What is the nature of the soil on which you 
have planted potatoes this year ? 
2. What crop preceded the potatoes ? 
3. What was the preparation of the land, and 
what manures were used ? 
4. What variety of potatoes were planted, and 
were the varieties early or late ? 
5. What was the date of planting ? 
6. What was the exact date of the appearance of 
the rot ? 
7. What varieties seemed to suffer least from the 
disease ? 
8. What proportion of the crop was destroyed ? 
9. On first noticing the rot, what was done to 
save the tubers, and with what result ? 
10. Following a clover-crop, how are potatoes 
affected by the rot, particularly badly or not ? After 
potatoes does clover do well ? Have you observed 
any fungus upon clover ? 
11. Following a wheat, oat, or rye crop, how are 
potatoes affected by the rot ? Where wheat, oats, 
or rye follow potatoes, what is the result ? 
If the potato-plant actually does not produce 
oospores in this country and in Europe, it is much 
more likely to die out or exhaust itself, or to be 
kept down by unfavorable seasons. The oospores 
have greater tenacity of life under various condi¬ 
tions than the other spores. To show that some 
benefit may come from knowing where the oospores 
of a fungus are produced, the case of the lettuce- 
mold, as investigated by Dr. Farlow, is in point. 
The lettuce-mold is a true Peronospora , P. gangli- 
formis. Its oospores are found to be particularly 
abundant in Groundsel, ( Senecio vulgai-is ), a weed 
of common occurrence in lettuce beds. Accord¬ 
ingly the groundsel should be weeded out with 
great care. 
As to what is to be done about potato-rot, all the 
suggestions that Prof. Farlow offers, in the present 
state of our knowledge, may be shortly given. 
“From what we have seen about the cause of 
the rot and the knowledge which we possess of the 
habits of the Peronospora , it is evident that there is 
no such thing as a specific against it. Whatever 
completely destroys the fungus, will also kill the 
potato itself. The object is to prevent as much 
harm as possible from being done to the plants, 
in which the mycelium already exists, and to pre¬ 
vent the spread of the disease to healthy plants. 
If we could control the amount of moisture in the 
air about the time when the disease is likely to ap¬ 
pear, say from the middle of July until the first of 
September, the mycelium would not increase to any 
extent to cause practically any harm. That we, 
unfortunately, cannot do ; and all that remains is to 
drain the land thoroughly, or to plant in a dry soil. 
Since the disease does not appear until about the 
first of August, the early potatoes should be less 
likely to rot than late ones. Exactly what variety 
a farmer should plant, is not a question to he de¬ 
cided by a botanist; but it should, at any rate, 
be a vigorous grower, and ripen as early as possi¬ 
ble, size and marketable qualities being equal. 
Certain varieties seem to resist the disease better 
than others, but as yet we know of none which may 
not be attacked. The precautions to be taken to 
prevent the extension of the disease, will be more 
definitely known when the plant in which the 
oospores are produced has been discovered.” We 
hope that some of the readers of the Agriculturist 
will consider the above questions, and at the proper 
time forward their replies to Prof. W. G. Farlow, 
Bussey Institution, Jamaica Plain, Mass. 
A Eustic Pot Cover. 
It often happens that one would like to bring a 
plant in flower from the greenhouse, to decorate 
the sitting room or dining room, or even to pro¬ 
mote a plant from the window to the table. There 
is nothing so well suited for the growth of plants, 
as a common flower-pot, but however clean it may 
be, a pot is an unsightly object, and its rude appear¬ 
ance much detracts from the beauty of the plant it 
holds. Considerable ingenuity has been expended 
in devising covers of various kinds. Handsome 
porcelain or other vases, within which the pot may 
be placed, can only be provided by the wealthy ; 
paper covers have been offered, but the dampness 
of the pot soon makes them limp and useless; the 
expanding cover, made of narrow strips of colored 
wood, which cross one another like a lattice work, 
answers a tolerable purpose, but still the pot shows 
through the openings more than is desirable. 
Messrs. Peck & Skilton, of Westfield, Conn., 
whose remarkably tasteful rustic work we have 
before noticed, seem to be on the right track, and 
make a pot cover which answers admirably for 
some uses. The engraving upon the next page 
gives a representation of the affair. If they will 
follow out the idea, and make covers of much 
lighter material, both in the body and in ornamenta¬ 
tion, we think that they will meet a want that all 
cultivators of house-plants must have felt. 
Culture of Cape Heaths. 
BY PETEK HENDERSON. 
In but few cases has there been in this country 
an attempt at growing a collection of those beauti¬ 
ful plants, the Cape Heaths. In all my experience 
I have only known of three cases, besides the one 
here referred to, where success has attended the 
attempt. But the desire to possess and cultivate 
what is novel and rare in greenhouse and hot-house 
plants is increasing. The visits of our people to 
Europe are now quite frequent, and a desire to do 
what is done abroad results not only in the impor¬ 
tation of novelties, but often in importing the skill¬ 
ed labor necessary to cultivate them. We have 
already many fine collections of rare Orchids, and 
other plants of the tropics, which are rather more 
easy of culture in our climate than in that of Britain, 
but the high temperature and dry air of our July 
and August have to be fought against if we would 
make Heath culture in our latitude a success. That 
this can be done, and has been done, a visit several 
weeks ago to the country seat of Mrs. John J. 
Mitchell, of Tarrytown, N. Y., most satisfactorily 
proved. The greenhouse and hot-houses form a 
curvilinear building of about 100 feet in leugth, 
with an octagon glass structure at each end of some 
60 feet in diameter ; in one of these octagon green¬ 
houses is a collection of about 80 distinct species 
and varieties of Cape Heaths, and some 20 of 
Epacris. The gardener in charge is Mr. Wm. 
Monroe, who for seventeen years was foreman to 
Methren & Sons, nurserymen, of Edinburgh, and 
brings to the work his experience in a section noted 
for successful Heath culture. Mr. Monroe regards 
the culture of the Heath as simpler here than in 
Europe, except in our hot summer months, when 
every means must be used to lower the temperature 
and at the same time increase the moisture of the 
atmosphere in dry days. To do this, the green¬ 
house must be so constructed that a current of 
air can be admitted at the lowest point of the front 
walls; that is, if the upright or front walls are 4 
feet in hight, one foot of the wall close to the 
ground must be open for ventilation, and at the 
highest point of the roof of the greenhouse a width 
of at least two feet should be made movable, to 
allow the escape of heated air. Besides this, to 
still further lower the temperature, a muslin shad¬ 
ing is placed outside, to prevent the sun’s rays 
passing though the glass. I emphasise “ outside ,” 
for every now and then we see shading placed upon 
the inside, which is nearly useless, if it is desired to 
lower the temperature of the house. In addition 
to shading, the paths are splashed with water, 
which both gives the necessary moist condition of 
the atmosphere, and lowers the temperature. We 
find that by judicious ventilation, shading, and wet¬ 
ting the floor of a greenhouse in the hot days of 
summer, we can reduce the temperature 10 degrees 
below that of the outside atmosphere in the shade. 
By these means, Mr. Monroe gets his Heath house 
tempered down, so that his plants are brought 
through the firey ordeal of our dog-days unscathed. 
As soon as the cool September days begin, there is 
no further trouble; the Heath is then of as easy 
culture as an Azalea or a Camellia, aud requires a 
treatment almost identical with them, so far as 
temperature is concerned. The soil necessary for 
the Heath and Epacris is peat and silver sand, or 
finely pulverized leaf-mold with sand might do 
where peat cannot be procured, but a soil of that 
soft character is indispensable, as the roots of these 
plants are as fine as hairs, and must have a soft 
medium to grow in. The specimens grown by Mr. 
Monroe were, some of them, 18 inches in diameter, 
and in the most vigorous health, and these too of 
kinds considered difficult to manage even in Eng¬ 
land. For example, here were fine specimens of 
Erica retorta major, E. PLartnelli, E. Maekiana, E. 
eximia, E. Masoni, and other rare species of which E. 
tricolor is the type, which to grow well is in Scot¬ 
land or England considered to be a triumph of hor¬ 
ticultural skill, and until now we believe has never 
before been so well done here. 
Of the softer and easier-growing kinds, such as 
E. ventricosa, E. hyemails , E. Wilmorei, etc., they 
were here by the hundred, “growing like weeds.” 
At the time of my visit many of the varieties were 
in bloom, and were well worthy of the extra culture 
required, not only from their great beauty, but 
from their rarity and novelty—qualities that may 
be looked for in vain in the collections of plants 
throughout the country. Is it not this rarity that 
gives the charm ? No matter how well the chromo 
imitates the painting, or the plaster cast resembles 
the sculptured marble, the ease with which they 
may be produced makes them cheap, and cheap¬ 
ness makes them common, and the charm of rarity 
is gone. It is said that the Duke of Devonshire 
once became the possessor of a plant of great value, 
and on discovering that a duplicate of it existed, 
he purchased it at a great price and destroyed it, 
in order to have the pleasure of saying that he 
owned the only plant of its kind in England. Much 
as some may be disposed to deprecate the selfish 
exclusiveness that prompts such an act, it would be 
useless to deny that the same feeling, though in a 
less marked degree, prompts many others besides 
the Duke, and yet the results tend to elevating the 
taste for the higher achievements of horticulture. 
Mr. Monroe inteuds to show a collection of Heaths 
at the Centennial Exhibition, and he may do this 
with the assurance that no other collection of 
flora’s treasures there will surpass it in interest. 
Slitting down the Bark of Fruit Trees in 
Early Summer. 
The writer remembers his father’s doing this 
when he was a boy. Sachs, in his Text Book, 
speaks of this as having been long ago advantage¬ 
ously employed in horticulture. Is the custom 
still kept up by orchardists ?—It is well known to 
those familiar with the microscopical structure of 
wood, that the outer part of each year’s layer, that 
is, the portion formed later in the season, consists 
of smaller wood-cells, and all flattened parallel 
with the bark. Now Sachs, (who likes to explain 
things mechanically), conjectures that this must ba 
owing to the pressure of the bark on the cambium 
or forming wood, which would increase as the 
growth of the season goes on. And in his last 
edition he states that DeVries has proved that it is 
so by experiment. So that this old practice ought 
to be useful, by enabling the trunk of a growing 
fruit tree to produce a greater amount of vigorous 
wood than it otherwise would do; and no harm is 
done when the slit heals promptly. a. g. 
