The Garden Under Glass

226 THE GARDEN UNDER GLASS very useful, for the young roots run easily into it, and are not torn when taken out, the fibre shaking readily from them. Mortar Rubble, Wood Ashes, Charcoal Mortar rubble is, of course, endowed with a considerable quantity of lime, from which most of the virtue will prob-ably have departed. Judging, however, by the way it is relished by fruit-trees, there must be a certain amount of nourishment to add to its mechanical value. I would advise its use for all pot fniits of any kind, and also for Chrysanthemums. It may be passed through a half-inch sieve, though for Chrysanthemums and for large fruit-trees it would be better to eliminate the dust afterwards by using a still finer sieve. When wood ashes are obtained from the burning of wood only they form a valuable fertiliser, but usually they are obtained from the garden smother fire, or the burning of all kinds of garden refuse, such as tree prunings, hedge triinmings, etc. Though they lose in value by this means, they are still rich in plant food, and should, after being sifted to get out all rubbish, be stored in a dry place. Charcoal is chiefly used for the purpose of keeping a compost sweet, and might well form a part of every com-post. It mixes better if broken so as to pass through a quarter-inch sieve. For all those plants which have to be content with the same compost for several years it is essential. Brick Dust and Sand These have none other than a mechanical value for open-ing and aerating the soil; though brick dust certainly holds