DECEMBER 25, 1875.] GREENHOUSES AND HOTHOUSES, The long winter of our Northern and Middle States tries the patience of our gardeners, and renders doubly accepta ble any hints and directions for the construction of green houses, wherein plants can be nurtured till the advent of spring; and where propagation can be carried on, so that a large supply of plants, both for flowers and fruit, may be ready for planting out as soon as the frost leaves the ground.