June 2, 1902.] Stipphment to the " Tropical Agriculturist »• 
861 
PLANT LIFE. 
[a series of simple lectuees intended fob 
A CLASS OF JUNI.ia STUDENTS.] 
Lectud.e V. 
Let U!* now enquire what, plants tnke up from 
the soil by way of fond. To begin with, we mii.«t 
recognise that the food of plants as taken up 
from the soil consist of more or less soluble com- 
pounds spoken of as salts. There are com- 
pounds produced by the action of an acid (such 
as nitric acid) upon a base (such as potash). lu 
this way we get suits such as nitrate of potash, 
or as it is better known "Saltpetre." This last 
mentioned salt is otie of a class of similar com- 
pounds (salts) which, as I have already stated, form 
the food of plants. Some of these salts though 
present as a rule only to a small extent are essen- 
tial to the life of the plant ; others which are 
generally met within the soil are not indispens- 
able though useful to plants. Those which are 
essential are the salts of potash, magnesia, lime, 
iron, and in addition phosphorus and sulphur. These 
which are useful though not indispensable are the 
salts of soda, silica, manganese, together with 
chlorine and occasionally other ingredients. What 
salts these substances form will of course depend 
upon the acid with which it combines, whether 
nitric acid, sulphuric acid, or any other acid. 
Thus we will get nitrates, sulphates, and so on. 
To attempt a fuller explanation of this part of 
thesubjt'Ct will be going too much into chemistry, 
which at present we must avoid. What I have 
told you will, Lthink, snlHce to make you under- 
stand the nature of the food taken by plants 
from the soil. The most important of the salts 
referred to above are the nitrates, because they 
supply what we may say is more important than 
any other of the elements of plant food, viz., 
nitrogen. If you ask why certain elements are 
essential as plant food, 1 can only s:iy that it 
has been proved by actual experiment that plants 
will not grow and flourish without them. The 
exact place which they fill in the plant economy 
is difScult to make out, though some scientific 
men appear to have found that they are required 
for certain ends. For instance, nitrogen, we are 
told is an essential constituent of protoplasm 
(that, is the livmgi part of plants), and since 
without nitrogen there can be no protoplasm, 
without protoplasm there can be no plant. 
Potash is said to be necessary for the full assi- 
milation of the carbon, which, we have seen, 
is derived from the air in the form of carbonic 
acid gas. Eecent experiments, also tend to shew 
that without potash no starch can be formed, and 
starch, you should know, is of primary importance 
in the nutrition of plants. 
Both sulphur and phosphorus are found asso- 
ciated with protoplasm. Phosphorus is believed 
to be needful in the formation of the pollen or 
fertilizing powder in the flower, and in the ripen- 
ing of seeds. 
Iron is essential to the formation of leaf-greeu 
or chlorophyll, which is essential to the produc- 
tion of starch. 
Though the precise function of lime is not 
known, it is of the greatest importance at least 
in keeping up the supply of the other essential 
iiigredif uts. The sub.stances already mentioned luid 
ot hers not JiUiidHd to, though not diiectly con- 
cerned ii. nutrition, yei are so indirecly, liy caus- 
ing cliMiige-in tl)e soil, by rendering some matters 
soluble and capable of absorption by the plant, 
by storing up and preventing the w;iste of in- 
gredients useful as plant food, and so on. But 
we are again going rather outside the scope of 
our subject. 
Plants are known to take their food in certain 
proportions, and cannot be induced to fu vour a 
particular substance^ because it is supplied or is 
present in the soil in large quantity. This would 
seem to indicate the existence of a power of selec- 
tion as regards food, but is explainable by the 
varying absorptive capacity of plants ; so that by 
virtue of such varying absorptive and digestive 
powers, plants take what they want and when 
they want it, and are not induced to take more by 
additional supplies. 
GENERAL ITEMS. 
According to the Jamaica Agricultural Society''s 
Journal there is no difference whatever between 
the two pines known as smooth Cayenne and 
Giant Kew. A variety, apparently a ne w one, as 
being unknown in Jamaica, that should be worth 
cultivating is the " white Guatemala spineless," 
thus described by Mr. J. C. Harvey who says that 
it was introduced into Mexico from Guatemala. 
It is absolutely smooth and has much the appear- 
ance of smooth Cayenne, that is to say the plant. 
The latter has a few short spines at the end 
of every leaf and the flesh is yellow ; this 
new pine has absolutely no spines whatever 
and the flesh is alm ost snow white — sweet but 
with a slightly sub-acid yet not stinging taste. 
The fruit is smooth and not conical — in fact per- 
fect in form— and reaches with practically no 
cultivation 7 lbs. Tlie core is never woody, 
and as it keeps well should prove a good market 
pine. The plant seems to be particularly adapted 
to heavy soils and damp situations. 
In some of the largest and most successful 
pine apple plantations in Florida, the soil is almost 
a pure sand containing as much as 99 % silica. 
It is said to be a mystery how pines grow in 
such a soil and yet they do grow. At the School 
of Agriculture, where the soil is particularly 
sandy, the pine apples have been doing very 
well, and all through May bore a good crop of 
fruit. 
The Paris Exhibition, where Ceylon made such 
a good show, has for one thing benefitted the tea 
industry in the Island, for the custom of " five 
o'clock Ceylon tea " appears to be spreading in the 
French capital. It is to be hoped that advantage 
will be taken of the St. Louis Worlds' Fair to 
make a thorough representation of our products 
with a view to educating the great American nation 
to an appreciation of what is -'made in Ceylon," 
