jAKtfARY 2, 1882.] THE TROPICAL AGRICULTURIST. 
617 
gathered from limestone rocks or calcareous hills, for 
in Bnch native soils the naturo and proportion of the 
elements present determine many other conditions besides 
mere chemieal composition. Chalk, for instance, and 
limestone are, broadly speaking, both calcic carbonate ; 
they are identical in the chemist's eye, and yet to the 
tender touch of the living rootlet they arc all the world 
unlike. Tho detritus which tills the crannies and cor- 
ners of a limestono rock — and it is in such places that 
tho so-called limestono flowers love to dwell — differs from 
the detritus which fills similar crannies in granitic rocks, 
not in chemical composition only, hut in physical feat- 
ures as well ; tho bare surface of the ono rock has a 
wholly different touch from that of the other, the differ- 
ence being perceptible even to our gross sense, much 
more so to tho exquisitely tender filaments of the young 
spreading roots ; and theso things influence the vegeta- 
tion as much, or probably oven moio than the mere 
abundance or scantiness of this or that Bpecial chemical 
element. And every grower of alpines has been in turn 
disappointed and surprised at finding that often his 
favourites refused to grow in soil prepared in careful 
imitation of their native beds, but flourished grandly in 
quito other stuff. 
There is apparently suflicient evidence that some plants, 
as, for instance, Rhododendrons, will not grow in soil 
containing an excess of lime ; but we are in the pre- 
sent (piite in the dark as to the exact naturo of this 
antipathy. It has been suggested that the cause lies 
in the fact that a calcaroous soil always is or always 
tends to bo alkaline to an extent 110 other soil can be, 
since no other alkali exists in cultivated soils in such 
abundance as does lime. And I have heard of an in- 
genious gardenor, who affirmed that lie had made Rhodo- 
dendrons flourish in a chalky soil, by continually ad- 
ministering adoquato doses of acids ; I mention this, 
not bocauso I think the case fairly made out, but becauso 
it illustrates what I said just now about the complexity 
of questions relating to the chemistry of the soil. And 
in the samo connection, I may call attention to the 
statements which have been made more than once, to tho 
eilect that eulphato of ammonia is by far the best nitro- 
gen manure for these same calcareous soils. The explana- 
tion given is that tho ammonia becomes dissociated from 
the sulphuric acid (the two being previously combined 
in tho sulphate of ammonia) and oxidised into nitric 
acid ; thus tho manuro added to tho soil provides at once 
two acids to work upon and neutralise the alkaline con- 
stituents already present, whoreas if instead of sulphate 
of ammonia the other common nitrogenous manuro, nitrato 
of soda, be given, more alkali in tho form of the soda 
is thrust upon the already alkaline ground. I might 
quote many other illustrations, showing that in all theso 
matters wo have to consider lirst of all the effects of the 
substances which wo add as manure on tho manifold 
changes which are continually going on in cultivated 
soil; but 1 think I have said enough. 
So far I may seem to have been arguing against the 
use of adding special elements or particular substances 
to the soil; but in reality I have simply boeu striving 
to guard against too rash expectations and the incon- 
hidorato use of ohemica] means. For that spocial chemical 
bodies added to the soil, whether by acting on the soil 
wholly outside tho plant, or being absorbed into the 
plant, and working changes in its tissues, do affect the 
growth and vigour of particular plants, is a faot which 
cannot bo denied, hi proof of this we have over and 
abovo the rough experience of tho farmer, which has 
taught hiiu to use "no manuro for ouo crop and another 
for another, tho valuable elaborate experiments of Lav.es 
and tiilburt at Rothamsti I In tlieir experimental farm 
is to bo seen a portion of old pasture laud divided into 
a Dumber of plots, lor some twenty years or more each 
plot httboati with boom ohange, manured with ■ part- 
icular uniuiiro— this frith ammonia, thai with phosphates, 
and so on — and each year in each plot the proportion 
U plants formiug tlie crop of hay is accurately detenu- 
155 
ined. Tho result 6hows beyond question that particular 
substances favour, on the same basis of soil, under the 
samo general conditions, particular plants. In this plot 
tho leguminous plants, common in ordinary pasture, have 
boon drivon out of existence ; in that they have flourished 
and almost driven away the proper grass, and so on. 
Every gardener who studies tho record of these experi- 
mental plots can see in it the beginning of tho garden- 
ing of the future. He can see that hereafter, by diligent 
study, ho will acquire the power of giving to the soil 
of his favourites just the things they need in their 
struggle for existence. But it is only tho beginning he 
sees, and long years of diligent study must intervene 
between present ignorance and future fruition. 
The plots of Messrs. Lawes and Gilbert are all either 
of pasture land or bearing ordinary agricultural crops. 
What from a gardening point of viow is wanted, is a 
similar serios of experiments with our garden plants ; 
put tho experiments, to be of real use, must be care- 
fully and systematically carried out, and, that lurking 
fallacies may be escaped, must bo continued through a 
long series of years. Hasty and slovenly hap-hazard 
trials lead chiefly to mistakes. Until some such system- 
atic researches arc undertaken, I fear that a knowledge 
of chemistry cannot be of very great use to the gard- 
ener. He must continue to do what he does now — to 
dig into or pom into the soil a mixed manure contain- 
ing in abundance all that his favourites need, but con- 
taining also in abundance firings which they do not 
need, or which even do them actually harm. The waste- 
fulness of such a plan is clear to every one who thinks 
for a minute over the matter ; and the drains and sub- 
soil of our gardens could tell many a tale of the man- 
urial waste going on wherever flowers are grown. I 
have been into gardens where for many years past heavy 
dressings of farmyard manure have been dug into the 
ground year after year, and that for the growth, not of 
coarse vegetables, but of delicate flowering plants. The 
result has, I am free to confess, often been good ; but 
I have almost held my breath when I have thought of 
the awful waste which in such cases must be always 
going on. And sometimes the result has not been good ; 
rampant diseaso has made its appearance, and played 
havoc with the beauty before it bloomed. Nor is this 
to be wondered at. Every one knows that in the early 
6tages of the comparatively simple fermentation of an 
ordinary compost heap, the material is a deadly poison 
to the 'plants, for which, when thoroughly ripened and 
rotten, its violent effervescences all over, it will serve 
as most nutritious invigorating food. So it is also with 
the stover quieter fermentations going on beneath the 
surface of the soil ; of the multitudinous changes going 
on there, while many, especially the final ones, are 
beneficial, some, especially tho initial and grosser ones, 
aro directly harmful to the plant; and if these latter, 
as in heavy frequent manuring is likely to occur, be in 
excess, they may poisou the organism which it was in- 
tended simply to feed. Happily, as in the human race — 
though many if not most people eat more than they 
nm l — starvation works more harm, on the whole, than 
does over-eating, 60 among plants, far more blooms fail 
through want of adequate food than are cut oft by a 
too liberal diet ; but tho waste, both in the ono case 
aud the other, is an evil which the stern demands of 
economy must sooner or later make us take firmly in 
baud. There can, I think, bo no doubt that, did wo 
possess tho requisite knowledge, both the waste and iho 
attendant disease might ho avoided. DlHTHS, 
(To be continued.) 
Thk Royal CIakdkns in Sum.— We learn fr.un Mr. II. J. 
Murtou, late Superintendent of the itotniiic Gardens i>t Sin- 
gapore, that by tho time these lines are iu print, he will hayo 
left Singapore, and taken charge of the Royal (iardi us m 
Siaiu. Letters and Catalogues should there fore now be ad- 
dressed to him at ISungkok.— UjnUnrr.-' Clu\>ni<.U. 
