THE COTTAGE GARDENER. 
[March 21. 
330 
Resuming, from page 230, our consideration of the 
roots of plants, so far as science throws such light 
upon the subject as may he beneficial to the horti¬ 
culturist, we have now to offer a few observations 
which, we regret to know, are opposed to the opinions 
of some of our coadjutors. 
According to the usual acceptation of the term, 
the roots of plants do not emit excrements, yet it is 
quite certain that, in common with all the other 
parts of a plant, they perspire matters differing in 
their amount and composition in every species. The 
earth, in contact with the tubers of a potato fully 
ripe, we have found to contain mucillage, or gummy 
matter, and it has the peculiar odour of the tuber. 
That in contact with the roots of peas, also contains 
gummy matter, and smells very strongly of that vege¬ 
table; and the freshly up-turned soil where cabbages 
have been growing emits an offensive stench. If 
plants are grown in water, that water acquires im¬ 
pregnations differing with each species vegetating in 
it; and, in addition to these facts, every gardener 
knows that the vigour and luxuriance of a crop is 
influenced remarkably by that which immediately 
before pre-occupied the ground on which it is grow¬ 
ing ; and this does not arise from the previous crop 
having robbed the soil of constituents required by 
its successor, hut from its having something offen¬ 
sive. Thus, brassicas will not grow healthily upon 
soil where the previous crop was of the same tribe, 
but if the ground be pared and burnt they will grow 
luxuriantly; and the same occurs to ground ex¬ 
hausted by strawberries: if it be burnt and manured 
afresh, strawberries will grow as vigorously as upon 
fresh ground, but they will not do so if manure only 
is applied. 
The fact that the roots of plants do give out pecu¬ 
liar and varying matters to the soil which sustains 
them, aids to explain why one rotation of crops is 
superior to another, as well as why fallowing is bene¬ 
ficial. 
Fallowing gets rid by decomposition of any offen¬ 
sive excrementitious matters, as well as accumulates 
that which is desirable for plants; and one crop 
succeeds better after some predecessors than after 
others, because their exuviie, or matters thrown out 
by them, are to that crop more useful as food. 
Plants are very much benefited by having oxygen 
applied to their roots, being found to consume more 
than their own volume of that gas in twenty-four 
hours ; and when applied by Mr. Hill to the roots of 
melons, hyacinths, &c., the first were found to be im¬ 
proved in flavour, the second in beauty, and all in 
vigour. Everything, therefore, that promotes the 
presentation of oxygen to the roots of plants must 
be beneficial; thus we find, that frequently stirring 
the ground about them promotes their growth; for, 
in proportion as the soil is loose can the atmosphere 
the more easily penetrate it. Moist earth rapidly 
absorbs oxygen from the atmosphere, as Humboldt 
has demonstrated, hut dry soil does not; this affords 
another reason for frequently stirring the earth about 
plants during the droughts of summer; for well pul¬ 
verized soil admits the evening dews, &c., more freely 
than consolidated ones, and consequently dews will 
be deposited more within their texture, and moisture 
is more firmly retained in such pulverized soils, inas¬ 
much as that they are not so much heated by the 
sun’s rays, being more pervaded by the air, which, 
like all gases, is one of the worst conductors of heat. 
M. Schliiber has more recently published experi¬ 
ments upon this subject, and their results confirm 
those of M. Humboldt. No earth, in the following 
table, absorbed any oxygen from the air in which 
they were confined, so long as they were dry; but 
when moist, and confined in a similar bulk of atmo¬ 
spheric air for thirty days, they had absorbed its 
oxygen in the following proportions:— 
Per cent. 
Siliceous sand . 
1.0 
Calcareous sand. 
5.6 
Gypsum in powder . 
2.T 
Sandy clay . 
9.3 
Loamy clay. 
11.0 
Stiff clay or brick earth ... 
13.0 
Grey pure clay . 
15.3 
Fine lime . 
10.8 
Magnesia . 
17.0 
Humus (vegetable mould).. 
20.3 
Garden mould . 
18.0 
Arable soil. 
10.2 
Slaty marl . 
11.0 
Our floricultural readers will hear 
with no small 
pleasure, that the prospect of receiving a Yellow 
Geranium again brightens. The following extract 
is from a letter we have received from the active and 
intelligent Secretary of one of our 
tural Societies:—■ 
local Horticul- 
“In consequence of perusing your article on the 
best mode of sending bulbs, &c., to 
England from 
hot countries, I was induced to write 
to a near rela- 
tive—the wife of a missionary of considerable influ¬ 
ence, who has resided great part of his life in the 
colony of the Cape of Good Hope—asking her to 
make some inquiry as to whether the Yellow Gera¬ 
nium was really to be met with. Agreeably to my 
request she wrote to Natal, but the flower is not (as 
you supposed) to be met with in that part of the 
colony, nor could she then hear of it. On making 
further inquiry, she was informed by a gentleman 
(I am not certain whether a missionary or a mer¬ 
chant) that he knew of three places where the yellow 
geranium is to be found; and I am promised, at an 
early opportunity, some seed if it can be procured. 
Believing that you and your readers would feel inte¬ 
rested in this, I am induced to trouble you with this 
letter.” 
