You very likely wonder how the Wallflower or any other plant can grow upon the wall, for there is no earth to be seen--nothing but stones and crumbling mortar. But if we pull up one of the smaller plants we shall find earth clinging to its roots. Dry dusty earth has been blown upon the wall by wind, and has lodged in chinks and holes. Dust and soil, too, were mixed with the mortar when the wall was built; and dead leaves falling on it and decaying have produced a little more--for decayed leaves make earth or "soil." Wallflowers and other plants which grow on walls and rocks find very little soil sufficient for their needs. Most of the blossoms of the wallflowers upon this wall are of a golden yellow colour and are very sweet. Some of the blossoms are, however, a darker yellow than others, and here and there are petals which are quite brown. If we look at the garden behind us we shall see that Mrs. Hammond has several beds of Wallflower this year; it is a flower of which she is very fond. There are wallflowers of two different colours in her beds. One kind has bright golden blossoms, rather deeper in colour than any of those upon the wall; the other has flowers that are a rich dark brown. [Illustration: WALLFLOWER.] These plants are sturdier and more bushy than those upon the wall, and there are more flowers on each plant. The flowers are finer, too, and have a stronger scent. If Mrs. Hammond had wished she could have sown seed to produce many different shades of brown and yellow Wallflowers. She might also have had a purple Wallflower, and even a Wallflower of so pale a yellow as to be almost white. If you and I were clever gardeners and had plenty of time and patience, we could get purple or nearly white wallflowers from these yellow-flowered plants upon the wall. It would perhaps take us many years, but we should succeed at last. This is how we should set about it. Suppose that we wished to have a Wallflower nearly white. We should look carefully along the wall in spring, when the blossoms are out, until we found the very palest yellow blossom we could see. We should mark that plant, and when the flower was over and the seed was ripe, we should collect the seed. Among the plants grown from this seed we should choose again the plant that had the palest flowers, and should save the seed from _that_. We might have to go on doing this for twenty years or more, but in time we should have a Wallflower so pale as to be almost white. _Quite_ white we should never get our Wallflower, for no _pure_ white flower can be obtained from a yellow one. However pale our Wallflower might be there would still always be just a tinge of yellow or cream colour in it.