422 
THE TROF*ICAL AGRICULTURIST. 
[December i, 1891 . 
are capable of being united to produce all tbo differ- 
ent cneniical compounds that go to make up the 
countless forms of matter. The number of different 
combinations possible between these seventy elemonts 
is practically inhnite. 
PLEIUENT.tUV tXIMl'OSITION OP PLANTS. 
f). When we state what eloments any substance 
contains, we give its elementary composition. For 
example, sugar contains the elements, carbon, hydro- 
gen and oxygen j this is a statoinent of the elementary 
composition of sugar. ,So, when wo state what 
elements a plant contains, we give its 
elementary composition or analysis. The term ulti- 
mate composition means the same as elementary com- 
position. We will now consider the elementary com- 
position of plants. , , . 
(5. The exact number of different kinds of plants 
growing on the earth has never been definitely ascer- 
tained: but the number probably exceeds 2tK),lK)0. 
Of this large number, only a few have been subjected 
to careful chemical analysis, and yet, so uniform 
in all its great variety are nature's methods of work- 
ing and building, that we can quite safely say that, 
so fares the elementary compositiuii of plants is con- 
cerned, little remains to be learned. Chemical analysis 
shows that, of the seventy elements known to exist, 
only fourteen are essential to produce all the differ- 
ent forma of vegetable life. 
While all plants contain certain chemical compounds, 
such as cclliuoae, albuminoids, etc., it may be that each 
plant contains, in some one or all of its parts, one or 
more chemical compounds peculiar to itself, so that 
there may bo ns many distinct chemical compounds in 
the vegetable kingdom as there are different species 
of plants. This, of course, cannot bo known absolutely 
until all plants in existence liave been carefully 
analysed ; but, whether the number of different 
chemical compounds in the vegetable kingdom be a 
few thousand or a few hundred thousand, wo know 
that they are almost entirely made up of fourteen 
olemouts, and these, therefore, form the chemical 
alphabet of the vegetable kingdom, all the different 
vegetable conipoandri, like %voi*da from lottery, being 
formed by the union of twooriiioro of these elements. 
The fourteen olomonts which are regarded aa being 
nocesaary to the perfect growth and development of 
every plant are the following : Carbon, hydrogen, 
nitrogen, oxygen, pboaphorus, sulphur, chlorine, silicon, 
calcium, iron, magnesmin, nuingauese, potassium and 
sodium. The element fluorine is of frequent occur- 
rence in very small quantities, and the following 
elements are of rare or doubtful occurrence : Alumi- 
nium, barium, bromine, cobalt, copper, iodine, lead, 
lithium, nickel, rubidium, tin, titanium and zinc, but 
their occurrence is a matter of curiosity rather than of 
practical importance, for, unlike the fourteen named 
above, they seem in no way to bo necessary to plant 
life. 
A1H-1)KH1VKI> ANn SOIL-DEUIVFD ELEMENTS. 
7. Tho elemonth that are necessary to the growth 
of plants may be divided into two quite distinct classes, 
which have important and marked diflcrenceB. These 
two classes are: ( 1 ). Air-dorivedor organic elements. 
( 2 ). Boil derived or inorganic elements. 
AIR-I>KUIVKI> elements. 1 SOIL-nEUIVRD ELEMENTS. 
Carbon. 
Hydrogen, 
Oxygen. 
Nitrogen. 
Phosphorus. 
Sulphur. 
Clilorine. 
Silicon. 
Calscium. 
Iron. 
Potassium. 
Sodium. 
IMagnosium. 
Manganese. 
8. It is usual among writers on agricultural chemis- 
try to call those classes organic and inorganic ole- 
monts, hut this use of these words is extremely in- 
accurate : for any element may bo cither organic or 
inorganic, according as it is or is not a part or pro- 
duct of an organized body. Oxygen, as it exists in the 
air, is inorganic matter; but when, through vital pro- 
cesses, it becomes part of an animal or plant, it is 
organic. 
9 . Those two classes of elements differ in throe im- 
portant particulars, as follows: — 
First. — The elements of tlie first class are derived 
exclusively from the air, either, directly or indirectly ; 
wliile those of the second class come exclusively from 
tho soil. 
Second. — Air-derived elements disappear, for the 
most part, in the form of gases, when a plant is 
burned; while the soil-derived elements, usually the 
smaller part, are left in the form of a residue or aah, 
which further heating will not have any effect upon. 
Some carbon and oxygen and nitrogen are always 
found in the ash, while alight quantities of chlorine, 
sulphur and phosphorus arc apt to bo driven off by 
heating. The two classes of elements are, therefore, 
not HO sharply dotined in this regard as they are in 
respect to tho Hourcea from which they come. 
Third. — These two clusaos differ very noticeably in 
regard to the quantities in which they are present in 
plants. Thus, the air-derived elements constitute, at 
least, ninety-five per cent, of the whole vegetable 
kingdom, while tlio soil-derived elements occur in 
small quantities, varying from a fraction of one per 
cent, lip to ten per cent., or even more in aomo cases. 
Because the soil-derived elements occur in so much 
smaller quantity, it does not follow that their presence 
ia of less importance : in their absence, vegetation 
would disappear. 
We will now consider each of those elements in 
order, and mention briefly some of the more im- 
portant characteristics of each ; but, befor doing 
this, it is desired to explain tho moaiiing of two or 
three chemical tenns which we sbaU have occasion to 
use. 
AOID-EORMINO EI.EMENTS AND METALS. 
lU, Of the fourteen elements which aro found in 
plants, Home are spoken of as nou-metallic elements 
or acid-forming olemouts, because, in certain coiu- 
hinatiouH, those elemonts form well-known acids. The 
other elements are known as metallic elements or 
metals. 
ACin-EORMINO elements. 
C’arbon. 
Hydrogen. 
Oxygen. 
Nitrogen. 
J’hosphoruB. 
Sulphur. 
Chlorine. 
Bilicon. 
METALS. 
Calcium. 
Potassium. 
Sodium. 
Iron. 
MagncBinm. 
Manganese. 
ACIDS AND HALTS. 
11 . Anacidis a compound containing an acid-form- 
ing clement combined with hydrogen and oxygen, or, 
in some cases, with hydrogen alone. Tho following 
examples will serve to illustrate: — 
Nitrogen, hydrogen and oxygen form nitric acid ; 
phosphorus, hydrogen and oxygen form phosphoric 
acid; sulphur, liydrogen and oxygen form sulphuric 
acid; chlorine and hydrogen form hydrochloric acid. 
'I’ho common name of sulphuric acid is oil of vitriol ; 
the common name of hydrochloric acid is muriatic acid, t 
12. A salt is a compound formed by putting a inota, 
in the place of the hydrogen of an acid; that is, a 
acid differs from a salt simply in having a metal where 
the acid has hydrogen. Kvery acid lias a salt corres- 
ponding to it. |«'or example, as staled above, nitric 
acid consists of nitrogen, hydrogen and oxygen. Now, 
if we put tho metal potassium in tho place of hydrogen, 
we have a compound containing nitrogen, potaHsiuin 
(in place of nyi.*ogen) and oxygen. I’kis com- 
pound is the potassium salt of nitric acid and is called 
potassium nitrate, or, sometimes, nitrate of potash. 
Again, phosphoric acid consists of phosphorus, hydro- 
gen and oxygen; in place of hydrogen, put one of the 
niotalfl, a.s calcium, and we have a compound contain- 
ing phosplioruH, calcium (in place of hydrogen) and 
oxygen, which is the calcium salt of phosplioric acid 
and IS called calcium phosphate, or, sometin'cs, phos- 
phate ol lime. Similarly, if a metal, as magnesium, is 
put m the place of tho hydrogen of sulphuric acid, wo 
have the uuignesiiuu salt of sulphuric acid, or maguc- 
