In the various designs which we present our readers in this volume, nearly all of which have been erected under our superintendence, and are now in operation, the manner of construction can be judiciously economical, or it may be elaborated to the most substantial and ornamental structures of the class to which they belong. There is no more reason for making these buildings of a temporary character, than there is for putting up our barns and other outbuildings in a cheap and unworkmanlike manner. The enjoyment of a country place naturally depends very much on its neat and tasteful appearance, the completeness of all its appointments, the order and good taste of all its arrangements. And although we do not advocate extravagance, or needless cost in ornamentation, which would be unsuitable to the purpose for which these structures are designed, we think that true economy would indicate the use of the best materials and workmanship requisite for substantial and permanent buildings. Horticultural buildings are not intended for a few years' use merely. Their profit, and the enjoyment they afford, will last for many years, and may be transmitted, with the other improvements of the country seat, as substantial and attractive appendages, indeed, as real property, worth all the money they cost, to the future proprietor.

There is still much to be learned in the matter of exotic grape-growing in this country, and, in fact, in the management of conservatories, orchard-houses, and all descriptions of horticultural buildings, and all classes of plants cultivated under glass. Whatever progress may have been made abroad, where experiments are carried on upon a large and costly scale, and often with eminent success, is of little or no value to the American horticulturist. Our climate is very different in its character and conditions from that of Europe, and especially that of humid England. We have, what they lack, real sunshine, with clear skies. Under the English methods of treatment, our graperies and green-houses would speedily be ruined. Nor are we willing to accept as final and conclusive the present best-known methods of vine culture. If there are better modes of managing exotic or native vines, and of developing the whole theory of grape culture, we shall be quite sure to find them out in the wide sweep of experiment which we are boldly and patiently undertaking in various parts of the country.

We do not propose, in our present work, to enter upon the investigation and discussion of the various theories of heat, light, color, radiation, &c., which properly belong to scientific treatises on these subjects. We intend to give only practical examples and results, from an extensive professional experience, with numerous designs and plans of buildings, most of which are now in successful operation, with the expectation that this volume will contribute not only to the general information of our horticulturists, and of gentlemen who are establishing themselves in the country, but also to create and encourage a taste for this kind of culture of exotic and delicate fruits, as well as the exquisite but tender gems of the floral world. When we find that we can command, at comparatively small cost of money and attention, the beautiful and luscious fruits of southern and tropical climes—their rarest and choicest flowers—the most delicious grapes, the finest peaches, nectarines, and apricots, the fig, and the pineapple, if we will; and that we can command these in abundance, to load and adorn our tables daily, the time cannot be distant when horticultural buildings, of various descriptions, will be found on all our country places or attached to our city homes.

POSITION OF HOUSES.

For lean-to or single-roofed structures used as forcing-houses for grapes or other fruits or plants, a southern aspect is generally preferred. Our own preference would be a position facing South-East, on account of the advantage gained from the morning sun, which is so favorable to the health and growth of all descriptions of plants. Although an hour or two of the evening sun might be lost to a building in this position, yet the rays are then comparatively feeble, and this loss would be much more than compensated by the more genial morning light.

Cold Graperies, with span roofs, and glazed at both ends, are better placed North and South,—that is, with the ends facing these points,—as nearly as a due regard to the positions of other buildings in the vicinity, and the general symmetry and apportionment of the grounds will permit. Each side of the roof will thus receive an equal amount of sun-light. For span-roofed Green-houses the rule is not so arbitrary, the glass not being lined with foliage, as in the case of graperies, the diffusion of light would not be materially obstructed. Under some circumstances, Green-houses may be placed east and west, as when a portion of the house is to be devoted to the purposes of propagation. The north side can thus be advantageously used, being less exposed to the sun's rays. Many plants requiring partial shade, would find there, also, the most favorable conditions for their cultivation.

Green-houses or Conservatories attached to dwellings, will answer in almost any position that convenience may require, or the taste suggest, as they are generally not so much intended for the growth of plants as for their display when in bloom. The sun should shine upon them, however, at least half the day. When they are intended for the growth of plants, then the more sun-light they can have the better.

FORMS OF HOUSES.

Until within a few years past, the straight-pitched roof, both single and double, has been used almost exclusively in the construction of glass houses. That there is an advantage in this form over some others, on the score of expense, and because there is less skill required in the builder, we admit, but there the advantage ends. The superiority of the curvilinear form is now beginning to be very generally acknowledged, on account of its being more graceful and pleasing to the eye, and because of its superior adaptability to the growth of plants. When to the curved roof is added the further improvement of circular ends, as illustrated in some of the designs furnished in this work, we have secured forms of houses that will admit double the light of the old-fashioned, heavy sliding sash structures which were built twenty-five years ago. Happily these old glass houses are fast falling into decay, and but few new ones are erected on their model.

Curvilinear roofs possess advantages over those of a straight pitch which may be briefly summed up as follows: