274 
THE COTTAGE GARDENER AND COUNTRY GENTLEMAN, Febbxtaet 5, 1861. 
merely for greenhouse plants in winter, a small iron store with 
a smoke-nipe through the roof, and with a flat head, so that 
you could* set a vessel of water on the top of the stove. To 
grow stove plants in winter, a similar stove, made with a top 
containing four or five inches deep of water, and two small 
galvanised iron pipes three inches in diameter communicating 
with the top as a boiler, would be the most economical mode. 
See papers on “Forcing.” We should only deceive you, 
however, if we were to attempt to give you a list of flowering 
stove plants that would do well without sun, especially when 
flowering and ripening their wood; hut if you gave the necessary 
heat, fine-foliaged plants, like the Dracaenas, Cissus discolor, and 
the fine-foliaged Begonias and Ferns, would answer extremely 
well, and look beautiful from the sitting-room. Much might he 
done in the same way with greenhouse Ferns and hardier 
variegated plants, merely with a temperature in winter of from 
40° to 45°. To grow the other things mentioned above the 
temperature in winter should rarely he below 55°, and would he 
better at 60°. See “Doings of the Week” as to frosted or 
decaying Geraniums.] 
HOT-WATER PIPING REQUIRED. 
How many feet of four-inch piping will it take to heat a span' 
roofed greenhouse, length 25 feet, 15 wide, and 11 feet 6 inches 
high ? I say not less than 180 feet.—A. P. 
[Quite right—from 160 to 200 feet. It is better to have a 
little more than is absolutely needed.] 
THE SCIENCE OF GARDENING. 
(Continued from page 227.) 
We shall confine our special remarks upon the diseases of 
plants to one class, for it is the only one towards which scientific 
investigation has been directed. 
Canker and Ulceb. —Whatever may be the disease under 
which a plant is suffering, it is fop usual for the cultivator to 
confine his attention to the part immediately affected. It is 
looked upon as a strictly local derangement, and the remedies 
are as erroneously topical. To consider that because a bud, 
a branch, or a root is diseased, that the cause of the disorder 
is to be sought for there, is as sensible as to suppose that every 
local pain endured by the human frame arises from a dis¬ 
organisation of that part. On the contrary, we know that the 
diseases of animals arise almost universally from the stomach; 
and, as Addison remarked, “ that physic is generally the sub¬ 
stitute for temperance or exercise.” The functions of the 
stomach, by whatever cause deranged, render digestion imper¬ 
fect and the secretions defective; the bile is superabundant or 
deficient in quantity, and headache is the result; the liver is 
diseased, and it causes a pain the most acute between the 
shoulders ; the blood is ill elaborated, and eruptions are thrown 
out on the surface of the body. 
With plants it is the same. It may be laid down as an axiom 
without exception, that all vegetable diseases, unpreceded by 
external injury, arise from the unhealthy state of the sap—a 
state brought about conjointly or separately by the deficient, 
excessive, or improper food imbibed, and the deranged digestive 
power of the leaves and other organs. That this is so will 
not appear strange when we reflect that from the sap all parts 
of the plant are formed, and are continually increased in number 
and size. The solid substance of the wood, and the temporary 
tender blossoms, are alike extracted from that circulating fluid. 
If the constituents for these are wanting, or if improper com¬ 
ponents are introduced, disease is the necessary consequence. 
Disease, which in youth and manhood usually arises from 
intemperance and over-excitement, visits old age as a conse¬ 
quence of its decayed vital powers; and, “if the silver cord 
has not been loosed,” or “ the golden bowl broken ” by the 
short-sighted indulgence of early years, man gradually declines 
into the grave, as the vital organs cease to perform their offices, 
because the limit of existence natural to his species has been 
attained. 
Some diseases peculiar to old age are prematurely induced 
in the usually vigorous period of life by indulgences individual 
or hereditary. Ossification of the vascular system is an example. 
In the vegetable part of the creation the canker or ulcer , to 
which our Apple, Pear, Elm, and other trees are subject, is 
a somewhat parallel instance. This disease is accompanied by 
different symptoms, according to the species of the tree which 
it infects. In some of those whose true sap contains a con¬ 
siderable quantity of free acid, as in the genus Pyrus, it is 
rarely accompanied by any discharge. To this dry form of the 
disease it would be well to confine the term canker , and to give 
it the scientific name of Gangrcena sicca. In other trees, whose 
sap is characterised by abounding in astringent or mucilaginous 
constituents, it is usually attended by a sanious discharge. In 
such instances, it might strictly be designated ulcer, or Gan¬ 
grcena saniosa. This disease has a considerable resemblance to 
the tendency to ossification which appears in most aged animals, 
arising from their marked appetency to secrete the calcareous 
saline compounds that chiefly constitute their skeletons. The 
consequence is an enlargement of the joints, and ossification of 
the circulatory vessels and other parts—phenomena very ana¬ 
logous to those attending the cankering of trees. As in animals, 
this tendency is general throughout their system; but, as is 
observed by Mr. Knight, “ like the mortification in the limbs of 
elderly people,” it may be determined as to its point of attack, 
by the irritability of that part of the system. 
This disease commences with an enlargement of the vessels of 
the bark of a branch, or of the stem. This swelling invariably 
attends the disease when it attacks the Apple tree. In the 
Pear the enlargement is less, yet is always present. In the Elm 
and the Oak sometimes no swelling occurs ; and in the Peach we 
do not recollect to have seen any. We have never observed the 
disease in the Cherry tree, nor in any of the Pine tribe. The 
swelling is soon communicated to the wood, which, if laid open 
to view on its first appearance, by the removal of the bark, 
exhibits no marks of disease beyond the mere unnatural enlarge¬ 
ment. In the course of a few years, less in number in proportion 
to the advanced age of the tree, and the unfavourable circum¬ 
stances under which it is vegetating, the swelling is greatly in¬ 
creased in size, and the alburnum has become extensively dead ; 
the superincumbent bark cracks, rises in discoloured scales, and 
decays even more rapidly than the wood beneath. If the caries 
is upon a moderately-sized branch, the decay soon completely 
encircles it, extending through the whole alburnum and bark. 
The circulation of the sap being thus entirely prevented, all the 
parts above the disease necessarily perish. 
In the Apple and the Pear the disease is accompanied by 
scarcely any discharge ; but in the Elm this is very abundant. 
The only chemists who have examined these morbid products 
are Sir H. Davy and Vauquelin ; the former’s observations being 
confined to the fact, that he often tound carbonate of lime on the 
edges of the canker in Apple trees.* 
Vauquelin has examined the sanies discharged from the canker 
of an Elm with much more precision. He found tills liquor 
nearly as transparent as water, sometimes slightly coloured, at 
other times a blackish brown, but always tasting acrid and 
saline. From this liquor a soft matter, insoluble in water, is 
deposited upon the sides of the ulcer. The bark over which 
the transparent sanies flows attains the appearance of chalk, 
becoming white, friable, crystalline, alkaline, and effervescent 
with acids. A magnifier exhibits the crystals in the forms of 
rhomboids and four-sided prisms. When the liquid is dark- 
coloured, the bark appears blackish and seems as if coated with 
varnish. It sometimes is discharged in such quantities as to 
hang from the bark like stalactites. The matter of which these 
are composed is alkaline, soluble in water, and with acids effer¬ 
vesces. The analysis of this dark slimy matter shows it to 
be compounded of carbonate of potass and ulmin—a product 
peculiar to the Elm The white matter deposited round the 
canker was composed of— 
Vegetable matter 
60.5 
Carbonate of potass 
. . . 34.2 
Carbonate of lime . 
5.0 
Carbonate of magnesia 
. 0.3 
100.0 
Yauquelin calculated, from the quantity of this white matter 
that was found about the canker of an Elm, that 500 lb. weight 
of its wood must have been destroyed.f There is no doubt 
that such a discharge is deeply injurious to the tree, but the 
above learned chemist appears to have largely erred ; for he cal¬ 
culated from a knowledge of the amount of the saline con- 
* Elements of Agric. Chemistry, 2nd. ed., p, 216, 
t Annules de Chimie, xxi. 30. 
