The other day, being in New York, I called over to see the new greenhouse erections that I had heard of being made by Peter Henderson, on Jersey City Heights, thinking they might interest some of your readers as they interested me. With your leave, I will give a brief description of plan and extent of this establishment that now covers a space of 300 by 400 feet, an area of 120,000 square feet, or nearly three acres of greenhouses and pits, and which, I presume, is now the largest on this continent. Mr. Henderson, as it is generally known, was one of the first to adopt and recommend the low, narrow span roofed pits, joined together on what is known as the "ridge and furrow plan," but this season he has removed all that was left of that class of houses, and has erected in their place sixteen houses, each twenty feet wide by one hundred long, and it is principally to describe these, that to me seem models of greenhouse structures, that I write this. I send a sketch of an end section, giving height of walls, etc, which will give an idea of how they are constructed.

Scale of one eight of an inch to a foot.

Scale of one-eight of an inch to a foot.

S. B. - Side Benches. P. - Pipes. M. B. - Middle Benches. W. - Walks. G. - Glass.

These sixteen houses, which form one ridge and furrow block, have their two outer walls built of hollow brick twelve inches thick, and that portion of the ends not covered with glass are also of brick; the inside gutters resting on brick pieces. Every foot of the wood work is of Yellow or Georgia Pine, both inside and out. One of the most important improvements in the construction of these houses is the construction of the benches, which are formed of heavy roofing slate,10x18 inches; these are laid on Yellow Pine bearers and covered with half an inch cement, so as to make them completely watertight, except at points where the water can be drained off at pleasure. These, Mr. Henderson assures me, have cost only about thirty per cent. more than the ordinary board benches, and he calculates that they will hold without repairs for twenty years.

The packing shed and offices, 350x20 feet are at the north end of this range, under the flooring of which are the boiler pits, and here a precaution is taken that is worthy of imitation,every boiler pit being arched with brick, resting on iron bearers, so that there is no possibility of fire occuring from the furnaces. The different temperatures necessary for the different classes of plants is graded by the number of pipes in each house, as all the houses are of the same size. That for tropical plants, such as Dra-cenas, Crotons, Palms, etc, have ten pipes in each house, giving an average night temperature of 70°; Bouvardias, Begonias, etc, eight pipes, average night temperature 60°; Tea Roses, such as Bon Silene, Niphetos, Pearl des Jardins, and others requiring high temperature, eight pipes, average temperature 60°; Pelargoniums and all classes of tri-color Geraniums, six pipes, average temperature 55°; Zonale Geraniums, Verbenas, and Petunas, five pipes, giving 50°; Roses and Carnations which are being kept dormant, four pipes, giving an average of 40°; this grading the number of pipes for the different temperatures, greatly simplifies the work.

These pipes are placed under the side benches, which leaves the large space under the centre table to be used for placing bulbs and such plants as do well in partial shade. In this new range are also the propagating house for cuttings, and propagating house for seeds. The cutting-house, 20x100, is shaded by the French Lattice Shadings, which are drawn up and let down by cords and pulleys from inside. These work so satisfactorily that Mr. Henderson proposes to use them next summer on all his houses needing shades. One greenhouse, 20x100, is used exclusively for seeds, and was to me, one of the most interesting features in the whole establishment, for I never before saw such a variety of delicate seedlings, so entirely free from fungus and damp. This exemption from damp, Mr. H. attributes to the use of these large and airy houses, where the air is never allowed to stagnate, for ventilation, less or more, is kept on at all times. The night temperature for both the cutting and seed propagation averages 60° at night with ten de grees higher in day time, slight ventilation be ing given in both at night.

On the right of the mid-entrance are four greenhouses, three of them 20x350 feet, and one for Summer propagating facing north, 10x350. The three large houses are built on the two-third span plan, that is, the long southern angle is some eighteen feet, the north angle nine feet. These houses are now filled with Roses, Poinsettias, Bouvardias, and such articles grown for Winter flowers. In reply to the question, whether he considered these houses with the long angle to the south, or those having equal span roof and with equal slopes to east and west, were best, Mr. H. said, that for choice he would prefer the houses with equal slope to east and west, though he did not think it very material which were used.

Although all of the greenhouses that are heated have fixed roofs, yet a block of six houses, each 100x11, are used without fire heat, in which all kinds of half-hardy plants and bulbs are heeled in sand, so that orders can be got at under cover in all weathers. In these houses, too, many plants are kept dormant until wanted to forward in heat, in far better condition than they would be if in sunk frames; for kept in these cold houses above ground they are kept dry - an important point with such plants in the Winter months. Although no vegetable market gardening is now done by Mr. Henderson, yet as a remnant of his old business, I found over 1,000 sashes covering cold frames, in which were planted hundreds of thousands of Cabbage, Lettuce and Cauliflower plants, these are grown to supply the smaller market gardeners, who have not yet the facilities for wintering themselves.

Large as Mr. Henderson's business now is, he informs me that, though he personally superintends it all, it is now done with far more ease than when it was only one-fourth the size. Everything is so systematized, that the responsibility is divided by the heads of the different departments; for example, the propagating is under charge of one man having three assistants; the potting-off, by one man with two assistants. One hand, specially attends to ventilating, one to watering, one to firing, and one to labeling. Then there is a corps of about twenty hands as order clerks and packers, and the balance of the hands are employed in the various duties pertaining to such a place. About eight or ten young men are always here under instructions, and are mostly young men of fair education and intelligence, for none others are received as apprentices. These usually remain from two to four years, and go out to take charge of some florist's establishment, or to begin business for themselves. It may be thought that this apprentice system if generally adopted would have a tendency to overstock the market with gardeners and florists, but if this standard of education was always insisted upon, it would tend to elevate horticulture, and thus popularize it in a way that could never be done if the majority of its members were mere diggers and delvers, which, it must be confessed, is the condition of the majority of our so-called gardeners in America today.