They each possess, too, an individual countenance, almost as varied when closely studied as that of a human being; not only can a shepherd distinguish every sheep in his flock, but we all know that each kitten in the successive families of our old favourite cat has a face of its own, with an expression and individuality distinct from all its brothers and sisters.

Now this individual variability exists among all creatures whatever, which we can closely observe, even when the two parents are very much alike and have been matched in order to preserve some special breed.

The same thing occurs in the vegetable kingdom.

All plants raised from seed differ more or less from each other.

In every bed of flowers or of vegetables we shall find, if we look closely, that there are countless small differences, in the size, in the mode of growth, in the shape or colour of the leaves, in the form, colour, or markings of the flowers, or in the size, form, colour, or flavour of the fruit.