1 Noy., 1901.] QUEENSLAND AGRICULTURAL JOURNAL. 453 
There are several kinds of gas, and that which escapes from a fire will not 
burn. Itis very poisonous to human beings who happen to breathe it in a 
close room, butit is one of the principal plant foods. 
In a future lesson J will tell you its name. For the present it is enough 
for you to know that a gas which comes from all fires, from candles and lamps, 
and even from your own breath, goes to form the different parts of a plant. 
How does the plant take in the gas? It takes it through the leaves. 
In the last lesson 1 told you that every little leaf has hundreds of little mouths 
always wide open during the day to take in food, like the little birds in their 
nests, whose beaks are always opened as soon as their mother appears with 
something to eat in her bill. 
All day long these little mouths are hard at work sucking in gas. Now, 
let us see what this gas does for the plant? To find this out, I must now tell 
you that when we talk about a plant we do not mean only a bean, or cabbage, 
or wheat plant, but also bushes, shrubs, grass, and trees of all kinds. Hvery- 
thing that grows in the soil or even on the bare face of a rock, the seaweed 
that clings to rocks on the sea shore, mushrooms, ferns, and everything that is 
not an animal or a mineral, belongs to what is called the vegetable world. The 
great gum-trees and ironbarks are vegetables, just as much as pumpkins and 
carrots, because vegetable only means something that grows from the soil. 
Well, then, our plant or vegetable has a root, a stem, branches, and leaves. 
_The food taken up in the water from the soil, together with the gas produced 
by fires, the breathing of animals, and by other means, combines to build up 
the stem, branches, and leaves. But here I must tell you that a very strange 
thing happens. The gas sucked in by the leayes is mixed with another gas 
contained in the air. Both gases are taken in by the plant, but only one 
remains there. The other goes out on its travels again after having seen the 
first safely deposited in the plant, where it helps to build up its solid parts. 
If it were not for the plants, which take in such a vast quantity of this 
poisonous gas, there would be a great deal of sickness in the world. There 
are some countries where men soon became ill and died until gum-trees were 
planted in the unhealthy parts, and they drew in all the bad gases, and those 
peces became quite healthy to live in. The gas which remains in the plant 
orms part of its food and becomes a portion of it, and can only be set free 
again by burning the plant or by its rotting away after it is dead. 
Now we will leave the plant for the present, and try to learn something 
more about what we call the soil. _ 
In the beginning, which was probably many millions of years ago, there 
was no such thing as what we now call soil. The world was at first nothing 
but a mass of rock and water. How then did all those rich fertile soils which 
you see everywhere throughout Queensland come into existence? They were 
produced in precisely the same manner as they are being produced now. The 
rocks, exposed to the air, to storms, rains, droughts, heat, and cold, gradually 
broke up. The great boulders were carried down into the valleys and gullies, 
where they were ground against each other by the rushing waters. Thus, 
gradually, they became reduced to fine sand, which spread over the low lands. 
The same thing happened on hillsides, where the rocks gradually decayed by 
the gas in the air acting upon certain parts of them, when they slowly broke 
up and formed beds of gravel and sand. Now, in all rocks there are some 
ingredients which largely go to make plant food, but they are useless to plants, 
because they cannot enter them until they are attacked by some other 
substance. They are like a gold or tin mine. The gold and tin are there, but, 
until someone comes along with plenty of money and machinery to dig them 
out, the mines might as well contain common stone for all the good they would 
do. ‘There is a word used to describe these ingredients of a soil. They are 
said to be “dormant’—that is, “asleep.” They want waking up, and the only 
way in which they can be waked up is by adding something to them which will 
stir them to activity—that is, make them ‘active.’ You have seen men 
making mortar for buildings. They have a heap of lime. ‘The lime is required 
