The necessity of more constant and perfect ventilation in houses devoted to the cultivation of the vine, has of late commanded the attention of some of our most skillful grape-growers, and has led to some improvements in the construction of vineries, which will no doubt be of great service to gardeners. In England, where the atmosphere generally contains much moisture, very free ventilation has always been given to vineries in moderate weather but in this country, where we have much hot, dry wind, we have been compelled to sacrifice our ventilation in order to retain the moisture in our grape-houses, often, no doubt, to the great injury of our vines.

The object of the present article is merely to call the attention of grape-growers to the scientific reasons which demand more constant and perfect ventilation than is ordinarily given to American graperies, and to suggest some means of accomplishing this object.

It is well known that leaves absorb from their under surfaces, and transpire or evaporate from their upper surfaces. Now, in a house which is not provided with sufficient ventilation, by a gentle current of fresh air passing through the vinery, and where a moist, heavy atmosphere is maintained, the function of transpiration from the upper surfaces of the leaves must be in a great measure, impeded, and hence engorgement of their tissues must take place. If the border be moist, the sap will rise With great rapidity and force, and the effete fluid matter, which ought to pass off. by transpiration, must pass very slowly, if at all, to the serious injury of the foliage.

Again, the pure natural atmosphere was made for plants as well as man, and any great adulteration or change of its chemical constituents) renders it poisonous to vegetable as well as animal life.

Plants, by their leaves, absorb carbonic acid gas, and discharge oxygen; but although carbonic acid is the natural food of plants, they can not exist in the presence of an, unusually large proportion of it, any more than man, who delights in oxygen, can endure a very great increase of that gas in the atmosphere without injury, or even the destruction of life. Carbonic acid gas benefits plants only when it does not exceed one-twelfth the bulk of the atmosphere, though one twenty-fifth is a still more favorable preparation.

In vineries, early in the spring, when little ventilation is permitted, is it cot probable that chemical changes in the atmosphere, very injurious to the vines, are often produced by unthinking gardeners, who take little heed of the great natural laws above-mentioned? The inside portions of vine borders frequently contain large quantities of carbonaceous matter in a state of decomposition, giving off carbonic acid gas with great freedom, and loading the unchanged atmosphere with a poisonous proportion of that gas in a few hours. Sulphurous add gas and ammonia, which are also often given off from the composts used in graperies, are equally as destructive to plant life, when in excess, as carbonic acid.

Oxygen gas, in large proportion in the atmosphere, is also highly injurious to plants. The change of color, which is seen in ripening leaves in autumn, is said to be due to the absorption of an excess of oxygen.

Hence it has been set down as an axiom in horticulture, that, other circum-stances being favorable, those plants are always the most vigorous and healthy which have the most liberal supply of pure natural air.

Another remarkable feet in the physiology and chemistry of plants is this: . that flowers and fruits, unlike leaves, absorb oxygen and give out carbonic acid quite freely, at all periods of their existence. Leaves, it will be recollected, as a general law, absorb carbonic acid and emit oxygen. The action of flowers and fruit, it will be seen, is just the reverse. In ripening fruit, especially, carbonic acid is very freely given out, while oxygen is absorbed; this is the case even in, fruit plucked from the tree while it is yet unripe.

These operations of nature are so delicate and complicated that man can not hope to imitate or regulate them, in an atmosphere of his own creating; and hence it follows, that only by free and constant ventilation can we supply to the vines that perfect and healthfiil atmosphere which has been provided for them.

But how shall we be able to supply a constant current of fresh air to our vineries, without too great a loss of interior moisture and danger of mildew? I answer, that some of the most successful vineries I have ever seen were very rude structures, the sides being constructed of loose boards, with numerous crevices for the admission of bottom air, and much ventilation had been given, by accident. In England, at the present time, great efforts are being made to introduce into vineries constant currents of fresh, warm air, by passing the air over heated surfaces. In this country, the suggestion has been made by Mr. Saunders and others, that constant top ventilation may be given in quite cool weather, day and night without danger, and that front or bottom ventilation may be given by covering the ventilators with coarse flannel, or loose woolen cloth, which, if kept constantly wet, would be all the better, admitting a steady supply of fresh air, and promoting ventilation without creating any injurious draught or currents of air.

The practical application of the principles stated, I leave for further experiment and discussion.

[The subject of ventilation, we apprehend, is a matter of more moment here than in England, owing to a marked difference in our atmosphere. There is a wide difference of opinion on this subject even among good grape-growers. While some are agreed as to the extent to which ventilation should be carried, they are by no means agreed as to the best means of effecting it. This is an open subject which can be profitably discussed, and we invite attention to it. We shall go over the subject in good time, simply remarking now that we regard top ventilation with much favor. Dr. Houghton, of course, will follow up the subject; he has left it at a provokingly interesting point. - Ed].