For most purposes it is desirable to use glass at least fourteen by eighteen inches, and for roses, sixteen by twenty-four will be none too much. In setting the glass, a good grade of putty or mastica is used under the panes. If it is to be lapped, it is held in place by means of zinc points or brads. For many purposes, however butted glass is preferred, the size generally being sixteen by sixteen. The square form is desirable, as it permits of the turning of the panes so as to secure a perfect union between them. When the glass is butted, it is customary to use wooden caps, over the sash bars, which are screwed down upon the panes. This makes a warm and water-tight joint and permits the ready resetting of broken panes.

In three-quarter span houses, the south wall should be about the same height as the walls of an even span house, but the north wall should be about one half higher, if the long-span-to-the-south construction is used, but both walls may be of the same height in the short-span-to-the-southhouse. The usual height of the ridge in a house twenty feet wide, is seven feet above the walls, except in a long span to the south in which the distance from the level of the south wall to the ridge is measured, and the ridge is so situated that the sash bars on the south side will be twice as long as those upon the north.

Either raised benches or solid beds may be used, the former being the most commonly employed for flowers and the latter for vegetables. In the construction of the raised benches it is desirable to use either gaspipe (Fig. 6) or angle iron for the supports, although if constructed of wood they will last a long time when supported upon bricks or cedar blocks. In order to secure proper drainage, there should be cracks of one half inch to one inch between the boards used for the bottom of the benches. In some cases, tile or slate bottoms are used and with an iron frame work, will form a very durable bench. The former practice was to place narrow benches along the side walls, with one or more wide benches in the center of the house, separated by walks, but in order to bring the benches into the more desirable parts of the house, the plan of having walks along the side of the house, and of arranging for three or four beds, from four to five feet in width, separated by walks twenty to twenty-four inches wide, has been adopted. With solid beds a similar arrangement has been followed, except that the beds are somewhat wider, although seven feet is the usual maximum for violets and carnations. The height of the solid bed is determined by the kind of crop to be grown and the distance to the glass. The same care is required as with raised benches to secure good drainage. This is generally done by filling in with broken. brick and similar material, and covering with eight inches of prepared

Where sub-irrigation is to be used, the bottoms of the beds or benches are made practically air-tight, and one or two lines of drain tile are placed lengthwise of the houses. The water is turned in at one end through a hose and, following the tile, makes its way out through the joints. In threequarter span houses with a long slope to the south, the benches are placed at different intervals, somewhat like a pair of stairs, so that those upon the north side will not be shaded, and that they will not be too far from the glass.

In sections where wood is cheap, a flue can often be used in small green houses, especially for the crops that require a moderately low temperature. If an arch with a fire-box measuring eighteen inches square and five feet long is placed at one end of the house, a flue twelve inches deep and eight to ten inches wide may be carried around a house not over fifty feet in length and brought back to a chimney built up from the top of the arch. When desired for houses more than fifty feet long, it is advisable to have an arch at each end. Where flues are used, care must be taken that the wood work of the house and benches is not in contact with their exterior. In some sections, ten or twelve inch sewer pipe may be substituted for the brick flue, but it should not be used within thirty feet of the arch.

For heating small ranges of green houses, some of the cast-iron hot water boilers, although they are comparatively high priced, will prove satisfactory and in the end economical, as they will be more durable than wrought iron boilers, especially if the latter are made in the form of box coils, from ordinary gas pipe. The joints of the latter being screwed together will expose more or less of the threads, and as a result, may not last more than two or three years, although with heavy pipe, the life of the pipe boiler may be seven or eight years, if care is taken not to have any of the threads exposed. For larger ranges where hot water is used, tubular boilers may be employed and will give good satisfaction, especially if the tubes are placed so as to fill the shell of the boiler. Although these boilers are made of wrought iron, the tubes are thicker than those commonly used for coil boilers, and the tubes being rivited rather than screwed into the boiler heads will be quite durable. Although not to be recommended for very small ranges, a considerable saving in the amount of pipe required for radiating surface in the houses can be made if the system is placed under pressure. Although there is hardly any limit to the size of the plant in which hot water under pressure may be used, a majority of greenhouse men prefer steam, for ranges of the size that will make the use of a night fireman desirable. While it will require rather more careful attention than a hot water system, steam as a means of heating greenhouses has