2174. Stages are shelves in series rising above each other, and falling back so as their general surface may form a slope. They vary in form according to that of the house. The houses with shed roofs and opaque ends have merely a series of steps reaching from one end to the other; but wherever the ends are of glass, by returning each shelf to the back wall, due advantage is obtained from the light furnished by the glass ends. The addition of ledgement, or turned-up edges, to each shelf, and the covering them with gravel, is, of course, as advantageous as in separate shelves, and surely more consonant with natural appearances, than leaving them naked like household or book shelves. Shelves and platforms of stone are now very general, and are found more congenial to the plants than dry painted boards.