[1] Get a chemist to make a solution of iodine and potassium iodide, which should be a bright, clear, orange colour.

[2] Weigh the plant, which you are putting in jar C, carefully, and keep a record of its weight for future use (see p. 18).

[3] This experiment is sometimes difficult to manage successfully, though it appears so simple. Great care should be taken not to overdose the plant with iron.

[4] Ordinary methylated spirit is rather impure alcohol, which will do if you cannot get any better.

[5] It is better to have half a dozen examples for each experiment, for the seedlings do not always act quite quickly and correctly, and from half a dozen you can see the average result.

[6] Spores are simple little structures which do much of the work of seeds. See the Chapter on Ferns.