The common Dittany, a perennial of the Mint family, with small, purplish flowers, in corymbed cymes or clusters, growing on dry hills from New York to Kentucky, is too well known to require any further description.

In August, we frequently observe a capsular body amid the ordinary fructification and flowers of this plant, which was first pointed out to me by Prof. S. S. Haldiman, desiring me to pay attention, and try to discover what insect produces the excrescence. Notwithstanding my desire so to do, I have not succeeded.

December 6, 1856, happening to pass through a wood of chestnut sprouts interspersed with the red cedar, near the Willistown Baptist Meeting-House, in Chester County, I observed the dry remains of stems, foliage, and fruit, of quite a number of plants of this species, with the expectation of finding, at this late season, the empty cells or larvae of the insect. I made diligent search, but could find no trace of such a pod-like excrescence. What, however, amply recompensed me for the attention bestowed, was the discovery that this plant is peculiar, and is truly a frost plant, far exceeding the Helianthemum Canadense, or Frost- Weed, as it is popularly called, from the fact that, late in autumn, crystals of ice shoot from the cracked bark at the root.

Our Cunila has attached to the stem a shell-work of ice, of a pearly whiteness, beautifully striated, sometimes, like a series of shells one in another - at others, curved round on either side of the stem like an open, polished, bi-valve; then, in others, again, curled over in every variety of form, like the petals of a tulip. Though one o'clock P. M., and the sun shining brightly, I carefully took up several specimens, and conveyed them three hundred yards, to the dwelling of Mr. Griffith, and exhibited the frost flowers to the family. No other herb or grass had any such frost-work around them, having paid particular attention; while at least fifty specimens of the Cunila examined, were so ornamented.

We naturally speculate as to the cause. On tasting the ice, no aroma was perceptible; the root manifested a vigorous young bud under ground.

Plants, in germinating, have the power of generating heat. That the atmosphere absorbs caloric from bodies, and deprives them of fluidity in the form of vapor, is well known and this vapor, congealed, we call frost. This heat is evinced by the more speedy melting of snow, when in contact with their leaves and stems, compared with what is lodged upon inorganic bodies, provided the preceding frost has been sufficiently permanent to cool those substances thoroughly.

Mr. Hunter has tested this fact by the rise of the thermometer; and Lamarck mentions an extraordinary degree of heat evolved about the time the Arum maculatum bursts its enveloping sheath. This is the case with our common Indian turnip - the Arum triphyllum also.

Though this may not be observable by our sensation of feeling, we are not to suppose it absent; even the thermometer only enables us to judge of the state in which the caloric is, with relation to surrounding bodies, without regard to its quantity.

That vegetation is not wholly suspended, however cold, as some suppose, is clearly proven by the experiments of Hales and Du Hamel; but there is a regular and gradual progress till the returning warmth of spring gives a degree of velocity to the juices, rendering their development more vigorous and apparent The power of cold on vegetables is well known, and, though the frosts of severe winters are, on the whole, more injurious to vegetation than those of spring, yet the latter are productive of more extensive damage, because their effects are evident almost every year. Frosts act more powerfully on ground newly cultivated, on account of the vapors continually ascending from such soil. Trees recently cut, also suffer more than others from spring frosts. Hence, likewise, light and sandy soil are thus more frequently damaged than tough land, though both maybe equally dry.

Although it has been generally believed that frost meliorates the soil, and especially clay lands, yet, as ice contains no nitrous particles, such improvements can only be of a transitory nature, by enlarging the bulk of some moist soils, and leaving them more porous for some time after the thaw; but when the water has exhaled, the ground becomes as hard as before, being compressed by the incumbent weight of the air.

To conclude, for the benefit of some I will add, that Mr. Baum found, by immersing quart bottles, filled with newly-distilled liquors, into a mixture of pounded ice and sea salt, for six or eight hours, the spirit proved as grateful to the palate as that which had been kept for several years. Geoffroy remarks that simple waters, also, acquire a more agreeable flavor after having been for some time exposed to the effects of cold. The effects on beef, poultry, etc., are known to everybody.

[Dr. Darlington, in his Flora Cestrica, says of the Cunila: "In the beginning of winter, after a rain, very curious ribbands of ice may often be observed attached to the base of the stems - produced, I presume, by the moisture of the earth rising in the dead stems by capillary attraction, and then being gradually forced out horizontally, through a slit, by the process of freezing."]