PATH OF LEAF-MADE FOOD DOWN THE STEM 39 
illustrated by raising a small quantity of, say, mustard, in a 
box until it is a few inches above the soil. If the box be 
now covered so as to shut off the light and a small hole be 
made in the side—the plants will bend over towards the 
opening. 
Summary of Lessons on Leaves. The work 
already done under this heading might be collected and 
summarised as follows-—shape of leaf—-colour—simple and 
compound leaves—position-—-function, 
NoTE.—It will probably be found necessary to reserve the work 
outlined in this chapter for Standard II. and higher classes. Pupils - 
should be brought to realise that air is able to enter the plant 
through its leaves—and that since air contains carbon-dioxide, 
which the leaves are able to decompose, and moreover since the 
leaves in order to form starch (of which carbon is a necessary 
ingredient) must be supplied with air, containing carbon-dioxide, 
it seems a reasonable inference that the air supplies the plant with 
carbon. The final proof of this fact is furnished by growing plants 
in culture solutions which do not contain carbon. 
The work here should not be hurried. The special teaching of 
every experiment should be clearly understood, and the bearing 
which each link has on the whole chain of experiments should be 
fully grasped—all this will require time. The work begun in 
Standard I. and Standard II. should be gradually extended in 
the higher classes, and revised in such a way as to show the 
connection between each successive step and those already taken. 
It is unnecessary to add that as much of this work as possible 
should be done by the pupils themselves. When conditions render 
this difficult, if not impossible, some of the pupils should be 
required to share in the work of the experiments—which ought to 
be carried out on such a scale that the whole class can follow and 
understand what is being done. 
IX.—_PATH OF LEAF-MADE FOOD DOWN THE 
STEM.—CuLtTurRE SOLUTIONS. 
Path of Leaf-made Food down the Stem. We 
have seen that the salt solutions obtained from the 
ground pass up to the leaves, and that the channels 
