During the present season a few remarks on the nature of restoring green-house and other tender plants which may be affected by frost, may not be uninteresting to some of the readers of the Horticulturist.

Every practical gardener is aware that the application of cold water upon frozen plants has a tendency to restore them; but from observation I am under the impression that, through ignorance of the nature of applying the water, it is seldom performed with that degree of success of which it is capable. Heat exists in two states, viz., latent and perceptible; when any two substances of different temperatures come in contact with each other, the temperature of the one is raised and that of the other is lowered, until the two substances become equal; and if they are of equal density the temperature will be a mean one; this is, provided that neither of those substances undergo a change from solid to fluid, or from fluid to gaseous. In this case, a great quantity of perceptible heat will be consumed and converted into latent heat; and if the change is from gaseous to fluid, or from fluid to solid, perceptible heat will be produced from the given off of the latent; thus, if equal weights of ice at 32°, and water at 172°, be mixed together, the whole of the ice will be melted, but the temperature of the mixture will be 32°, so that 140 degrees are lost, or converted into latent heat.

If a tender plant that will not bear the frost, a Heliotrope or Pelargonium, for instance, be exposed to an atmosphere of 32°, it will not be injured, but if the temperature sink below that point, say 28°, under ordinary circumstances, when there is the least circulation, the juices of the plant will become frozen, and it will be injured by the application of perceptible heat in its rising from 28° to 32°; but if the temperature, when at 28°, is raised by the freezing, when the act of freezing, by giving off latent heat, raises the temperature to the freezing point, the plant is uninjured.

It follows, therefore, that the application of water should commence before there is any alteration in the temperature of the surrounding atmosphere; that is, in the morning before the sun's rays shine upon the house containing the frozen plants, or before a fire is put on, and continue until the temperature is raised to the freezing point; but if the temperature of a green-house should be sunk to 28°, and a slight syringing of water applied only sufficient to raise the temperature by the congelation of its particles to 30°, a great injury will be sustained, if left to rise afterwards by perceptible heat to 32°, as the agitation which will have taken place among the plants will have more effectually frozen their juices.

The water which is used should be but little, if any, above the freezing point, or as cold as can be procured, so that the temperature of the plant should rise from 28° to 32°, not by the application of a warmer substance so much as the converting of latent into perceptible heat. It is also of very great consequence that the leaves or no part of the plant should be moved when in a frozen state, as the cellular tissue of which they are in a measure composed, being of a very-delicate texture, each cellule being filled with watery juice, which becomes frozen, the least bending of that part of the plant would rupture the membranes, which are only (and in many cases not quite) elastic enough to allow of the expansion of the water by freezing; it is, therefore, obvious that, instead of the water being laid on by a heavy rose, it should be done by a very fine syringe like a shower of dew.

I have put the above idea in as condensed a shape as possible; I hope not too much so to be understood.

[A very interesting subject, especially to those who keep plants in rooms. But even in the conservatory and the green-house we are sometimes " caught," as the gardeners term it. We have had Fuchsias, Pelargoniums, Dendrobiums, Cactae, and similar plants, frozen hard, the thermometer indicating 24°, and have recovered them all by shading the house and applying cold water gently through a very fine "rose." We have known the same thing to be done in a number of cases, and therefore conclude that the application of cold water is a good remedy to recover frozen plants. Great care must be exercised that no sunshine reaches them for some time afterward. - Ed].