among botanists, comprehends the precise time which the seeds take to rise after they have been committed to the soil.—The different species of seeds are longer or shorter in rising according to the degree of heat which is proper to each. Millet, wheat, and several of the grasses, rise in one day; blite, spinach, beans, mustard, kidney beans, turnips, and rocket, in three days; lettuce and dill, in four; cucumber, gourd, melon, and cress, in five; radish and beet, in six; barley, in seven; orach, in eight; purslain, in nine; cabbage, in ten; hyssop, in thirty; parsley, in forty or fifty days; peach, almond, walnut, chestnut, peony, horned poppy, hypecum, and ranunculus falcatus, in one year; rose bush, cornel tree, hawthorn, medlar, and hazel nut, in two. The seeds of some species of orchis, and of some liliaceous plants, never rise at all. Of seeds, some require to be sowed almost as soon as they are ripe, otherwise they will not sprout or germinate. Of this kind are the seeds of coffee and fraxinella. Others, particularly those of the pea-bloom flowers, preserve their germinating faculty for a series of years. Mr Adanson asserts, that the sensitive plant retains that virtue for 30 or 40 years.

Air and water are the agents of germination. The humidity of the air alone makes several seeds to rise that are exposed to it. Seeds too are observed to rise in water, without the intervention of earth; but water without air is insufficient. Mr Homburg's experiments on this head are decisive. He put several feeds under the exhausted receiver of an air pump, with a view to establish something certain on the causes of germination. Some of them did not rise at all; and the greatest part of those which did, made very weak and feeble productions. Thus it is for want of air that seeds which are buried at a very great depth in the earth, either thrive but indifferently, or do not rise at all. They frequently preserve, however, their germinating virtue for many years within the bowels of the earth; and it is not unusual, upon a piece of ground being newly dug to a considerable depth, to observe it soon after covered with several plants, which had not been seen there in the memory of man. Were this precaution frequently repeated, it would doubtless be the means of recovering certain species of plants which are regarded as lost; or which perhaps, never coming to the knowledge of botanists, might hence appear the result of a new creation. Some seeds require a greater quantity of air than others. Thus purflain which does not rise till after lettuce in the free air, rises before it in vacuo; and both prospers but little, or perishes altogether, while cresses vegetate as freely as in the open air.