Mr. Editor : - I confess myself somewhat mystified by the philosophic theory of your correspondent, Daniel Barker, in last month's HORTiculturist, on this subject; the reasoning is too profound for my apprehension. I can not follow him, and can only understand his deductions, from which I entirely disagree.

He says "it follows that the application of water should commence before there is any alteration in the temperature of the surrounding astmosphere:" by which is meant, I suppose, that on finding our plant-house frozen on getting up in the morning, we must not apply fire, but water. 1 am afraid Mr. Barker will find few converts to that doctrine, no matter how fine he may show it in theory - disastrous experience in practice is strongly against it. Wo will suppose that, on entering a green-house at six in the morning, we find the plants frozen, the thermometer marking 26 degrees, with an outside temperature below zero, and a high wind from the north; under such circumstances I have repeatedly seen the thermometer fall from 2 to 4 degrees before fire, with all possible speed, could be got to act on the flue or pipes. Would Mr. Barker, under such circumstances, still persist in applying cold water? If he did, he may rest assured that it would dissipate his fine theory and the existence of every tender plant at the same time.

I know that the opinion is very general that when plants are frozen they are benefited by being shaded from the sun's rays, and by gentle syringings of cold water; but with all deference to the belief, I must say that my own experience leads me to the conclusion that it is a doubtful remedy. We are too apt to receive a handed-down maxim of this kind as a fact, without investigation or experiment. Getting a house of plants frozen is always a serious and vexatious matter, and few have courage enough to experiment, but at once apply the popular remedy. And as a sick man may use a harmless quack medicine, if it results in a cure, (!) the medicine is lauded by the grateful patient; if he dies, he was too far gone for recovery. Just so with a frozen plant. If Jack Frost has laid his hand but lightly on, it will recover, medicine or no medicine; but if severe enough to rupture the cellular tissue of the plant, all the remedies in the world will not avail.

I had an excellent opportunity of testing this matter, on the night of the 5th of • February of last year - the coldest of my experience. Our means of heating were found entirely inadequate to keep out the frost; the consequence was that I had several of my green-houses frozen, two of them very badly, but as is usual in such cases, frozen only at one end of the house. Although I had no faith in the shading and sprinkling remedy, I resolved still further to confirm my unbelief.

One house containing Verbenas was shaded and sprinkled in the orthodox style, after the thermometer had reached 82 degrees. The other, containing Fuchsias, Geraniums, Heliotropes, etc., was left exposed to the sun's rays without sprinkling.

Now mark the result. In each house for the first four or five sashes, where the frost had struck severely, all were killed outright; in the next four or five sashes, some were killed, and some severely injured; the remaining part of houses being but slightly frozen, were nearly free from injury. The effects in each house were as nearly alike as they could be; there was no difference perceptible in the house where the remedy was applied, and where it was not.

But doctors differ, and 1 see, Mr. Editor, that I differ with your august self in this matter. But the next time you are unfortunate enough to get "caught" by our arch-enemy, make "two divides" of your parlor pets, faithfully and hopefully sprinkle the one lot, and leave the other unbaptized heathens, and give the result to your readers.

[We leave Mr. Barker to respond in his own behalf. We have stated our practice to consist in shading the plants, raising the temperature very gradually a few degrees above the freezing point, and then applying cold water. Our success has been almost uniform; Mr. Henderson confesses to a decided loss in both his cases; we therefore feel warranted in holding to our plan for the present. We mean, however, to give his a faithful trial at the first unfortunate opportunity. But his plan does not differ so materially from ours as would at first sight appear; for the coating of ice on the glass of a green-house forms a very good shade indeed, though in a bad case we should want something additional. Plants may undoubtedly sometimes be so frozen as to be past recovery; but we have no hesitation in saying, that our plan, faithfully observed, will in a majority of cases prove decidedly efficacious. We have here a fine field for experiment, but a costly one. Mr. Henderson's article was intended for our last number, but was crowded out. - Ed].