Page:The Works of Aristotle - Vol. 6 - Opuscula (1913).djvu/100

821$b$ they are young than when they are old; others, on the contrary, are more fertile when they are old, almond-trees, for example, and pear-trees and holm-oaks. Wild and garden plants can be distinguished by identification with the male and female, each being recognizable by its peculiar characteristics; for the male is thicker and harder and has more branches and less moisture and a smaller fruit, and as does not reach such maturity; the leaves, too, and likewise the twigs, are different.

After these considerations we ought to form some conclusions in order that we may know trees and their various kinds apart, and similarly in the case of small herbs. We must consider what the ancients have said on these points, and examine the works written upon them. We shall only be able to take a brief survey and extract the essence of them. This means that we shall consider those plants which contain oil, those which produce seeds, and those which produce wine, and plants which have medicinal properties, and those which destroy life. All these particulars about trees and plants are well known. But in order to know their causes, we ought to inquire into their production, and discover why certain plants grow in certain places and not in others, and at certain seasons and not at others; we must examine their methods of planting, their roots, their differences of sap and odour and juice and gum, and the excellence and defects of particular plants, and the fact that the fruits of some trees last but not those of others, and why some fruits putrefy quickly, others more slowly. We must inquire into the properties of all plants, and particularly those of their roots; and why some fruits grow soft while others do not; and why some affect the bowels, others cause sleep, and others are fatal to life; and many other differences.