140 
J'TEXAL OF THE RnY.AL HORTICULTURAL SOCIETY. 
OX PLANT COMPOSITION AND MANURIAL EEgUIREMENTS. 
By M. Georges Teuffaut. 
"Eead August 29. 1899.: 
If a plant be analysed, no matter from what part of the globe it may be 
derived, there are always found in it the same natural elements, although 
very diversely associated. These elements are carbon, oxygen, hydrogen, 
nitrogen, phosphorus, sulphur, chlorine, potassium, sodium, magnesium, 
siHcon. calcium, iron, manganese ; and more rarely zinc and copper, which 
appear only to be present in altogether special cases. 
In a general way it is the components of atmospheric origin — carbon, 
hydrogen, oxygen, and a portion of the nitrogen — which mainly enter 
into the constitution of plants. 
If, however, a plant be calcined in an open vessel, all the elements of 
gaseous origin disappear, and nothing is left but the mineral elements, 
which have certainly been furnished to the plants through the soil. 
The mineral aliments of plant life are therefore chlorine, sulphur, 
phosphorus, sihca. calcium, magnesium, iron, potassium, and sodium. 
In order to ascertain the form under which these different elements are 
susceptible of being absorbed by the roots of plants, it is well at the 
outset to define in a very general way the nature of vegetable soil and 
its original constitution. 
At the time when the earth's crus: first became solidified, it was 
solely constituted of various crystallme rocks in the act of solidifica- 
tion. These rocks contained all the mineral elements now distributed 
in nature, but the siUcates. whether of lime or of potash, of soda 
or alumina combined with oxide of iron, were by far the most abundant. 
We can weU imagine that the first external influences which were 
exercised upon these rocks were all chemical : the atmosphere, super- 
heated at this period, being extremely rich in carbonic acid. And the 
continuous fall of rain charged therewith attacked these rocks little by 
little, and rendered soluble, under the form of bicarbonates. a part of the 
lime, of the potash, of the magnesium, and of the other bases. 
The water, following the slopes, carried these bicarbonates away with 
it. Little by little the aerial pressure of the carbonic acid diminished, and 
these bicarbonates, losing the greater part of their carbonic acid, were 
transformed into insoluble carbonates. Ir is this phenomenon which 
permits of the explanation of the accumulation of enormous masses 
of either calcareous rock (carbonate of limei or of dolomite 'Carbonate 
of magnesia). 
There was effected, therefore, at this period a dissociation of the 
primitive rocks and a classification of their elements ; the clay, resulting 
from the silicates of alumina and hydrated potash, remaining imattacked. 
The silica, which also was generally unattacked, was transported by water 
to a greater or less distance, according to the size of the grains. There was 
thus formed either the siliceous sands, the tine mixtures of sand and clay, 
or the gravels, the original material of conglomerates, the stones of which 
were subsequently cemented together either by a calcareous cement or a 
ferrugineous one. This gives a very general idea of the origin of the 
