There has been already a great deal said on this subject; some say 40, others 50 degrees, is the best temperature for greenhouses. With me this month I keep as close to the above as possible, at night, - the former on dark cold nights, the latter in clear moonlight nights; and allowing the temperature to rise as high with solar heat as 80, and even higher before I ventilate; doing that with the top sash, and I do not believe it an injurious practice. Greenhouses lose considerable of their interest if they have little bloom, more especially private greenhouses.

By following my principles, you will have your house more gay and interesting during the dreary months when John Frost rules supreme, and you may go into your miniature garden and laugh him to scorn. But it must be remembered if there is a high temperature kept up, we must supply moisture freely by sprinkling or syringing. The closer we imitate nature the better. The night in the open air is almost invariably cooler than day; more especially the season we try to imitate. Plants grow more freely by day than by night: the night was made for rest, both for animals and vegetables, although there are a few exceptions in both cases. I have found that vegetation is more active in bright moon or full moon, requiring less fire to repel the same amount of frost. My attention was first called to this subject by the following facts, from my own observations. We have a conservatory thirty feet fronting south, twenty-seven fronting west. The sun had gone down in the western horizon, the glass in the sash on the south front gradually thawed as the moon wore round to the south.

I had noticed this circumstance long before, but always thought if was getting milder outside, or the flues were getting warmer inside: but I found I was mistaken, as the frost remained on the glass until the moon had gained a south-westerly position; then it began to thaw, at the same time commencing to freeze on the south front. The moon, in my opinion, acts the same as the sun, only to a lesser degree, in keeping up a high temperature. It requires a greater amount of care, but this comes at a season of the year when the gardener has the least to do. The nature and habits of the several species of plants, if possible, should be understood towards their proper management; thus supplying water equally to all, without regard to their stage of growth, or water supplied too freely in a state of inactivity, will rot the roots of most. When they are in an active state of growth, we should bear in mind the liquid manure, soap suds, etc.

I prefer raising the temperature rather than ventilating so early, as we lose so much warm moisture which is so genial to the growth of plants; always ventilating from the top if possible. In winter I have a potting room where I admit the air first, and it becomes somewhat tempered by the time it reaches the plants. I do not wish to be understood raising the temperature only in proportion to the light; in regulating plants upon stages it must be remembered that the top is the warmest, the lower the coldest; warmer air is lighter, the lower the colder; therefore one rises, the other falls. Also most plants kept in such structures come from a temperate climate. Yours, etc., John C. Ure.

Chicago, February 1,1859.

Dear Sir: - One of the greatest annoyances a gardener has to contend with is the ravages of insects upon young plants. I have a remedy which I have applied for several years, and have never known it to fail. Take three parts air-slaked lime, or unleached ashes, and one part Peruvian guano, or any other substance containing a large per centage of ammonia; mix them well together, and dust the plants while the dew is on them, and apply it after every rain; but care must be taken that too much is not used at one time, or it will hare a deleterious effect upon the plants; a light dusting is all that is necessary. I noticed the effect more particularly last spring, upon a patch of cantaloupe vines, which the yellow bugs were eating up. I dusted about one-half of the patch; the next morning there was not a bug to be seen on that portion of it, while they were literally devouring the other; but a dusting cleaned them all out in ten minutes so effectually, that I was not bothered again the balance of the season. I have found it to hold equally good for cabbage and other plants.

I do not know the effect, unless it is in the ammonia being set free, which, perhaps, is a little too strong for their olfactory nerves.

My impression is that it would be a partial remedy, at least, against the curculio. I have never tried it, as I have no plum-trees yet in bearing; but I intend trying it upon my apricots the coming season, and, as it appears to be the determination to not leave a stone unturned until a remedy is found, will not some of your numerous correspondents try this? It is simple, and easily applied, and would it not be quite a victory over the " little Turk," and very humiliating to him, after standing all kinds of fire, at last to be compelled to surrender to snuff?

Yours, truly, D. M. R.

Washington, D. C, Jan. 14th, 1859.