If a plant be frozen, and though some defy the attacks of frost, others are very liable to its fatal influence, death is brought upon them as it is in the animal frame, by a complete breaking down of their tissue; their vessels are ruptured, and putrefaction supervenes with unusual rapidity.

The following contingencies render a plant especially liable to be frozen.

"First. Moisture renders a plant susceptible of cold. Every gardener knows this. If the air of his greenhouse be dry, the plants within may be submitted to a temperature of 32° without injury, provided the return to a higher temperature be gradual.

"Secondly. Gradual decrements of temperature are scarcely felt. A myrtle may be forced and subsequently passed to the conservatory, to the cold-pit, and even thence to an open border, if in the south of England, without enduring any injury from the cold of winter; but it would be killed if passed at once from the hot-house to the border.

"Thirdly. The more saline are the juices of a plant, the less liable are they to congelation by frost. Salt preserves vegetables from injury by sudden transitions in the temperature of the atmosphere. That salted soil freezes with more reluctance than before the salt is applied, is well known, and that crops of turnips, cabbages, cauliflowers, etc, are similarly preserved is equally well established.

"Fourthly. Absence of motion enables plants to endure a lower degree of temperature. Water may be cooled down to below 32° without freezing, but it solidifies the moment it is agitated." - Principles of Gardening.

The seeds of some plants are benefited by being frozen, for those of the rose and the hawthorn never germinate so freely as after being subjected to the winter frosts.

Freezing is beneficial to soils, not only by destroying vermin within its bosom, but by aiding the atmosphere to pervade its texture, which texture is also rendered much more friable by the frost. M. Schluber says that freezing reduces the consistency of soils most remarkably, and that in the case of clays and other adhesive soils, the diminution of their consistency amounts to at least 50 per cent. In hoeing clay he found it reduced from sixty-nine to forty-five of the scale already stated, and in the ordinary arable soil from thirty-three to twenty. He satisfactorily explains this phenomenon by observing that the crystals of ice pervading the entire substance of the frozen soil, necessarily separate the particles of earth, rendering their points of contact fewer.

As soil in our climate is rarely frozen to a depth of more than four inches, and in extremely hard winters it does not penetrate more than six inches in light soils, and ten inches in those that contain more clay, or an excess of moisture, these facts, and the frequent failure of our potato crops, have led Dr. Lindley to the very judicious suggestion of planting these crops in autumn, which must be the best time if practicable, for it is pursuing the dictate of nature. That it is practicable, I have no doubt, for no frost would injure the sets, if a little coal ashes were put over them in each hole, for coal ashes are an excellent non-conductor of heat, and consequently opposed to a low reduction of temperature. Even if potatoes buried some inches beneath the soil's surface are frozen, they thaw so very gradually, that no injury to them occurs, unless the freezing has been sufficient to burst their vessels, which occurs very rarely.