Walls for hothouses

2102. Walls of some sort are necessary for almost every description of hothouse; for even those which are formed of glass on all sides are generally placed on a basis of masonry. But as by far the greater number are erected for culinary purposes, they are placed in the kitchen-garden, with the upper part of their roof leaning against a wall, which forms their northern side or boundary, and is commonly called the back wall, and the lower part, resting on a low range of supports of iron or masonry, commonly called the front wall.