. The life of the plant. Plant physiology. 12 THE LIFE OF THE PLANT With the naked eye, or, better still, with the help of a lens, a small germ plant, a young shoot, consisting of a tiny stem with leaves and rootlet, is easily recognised (fig. i). This shoot binds together the two halves of the seed, which are called the cotyledons. These, though much larger than the Fig. I. shoot itself, are nothing but two appendages of it. But what is the nature of these cotyledons? Botanists say they are leaves. Those colourless, round, fleshy bodies, which remain underground are called leaves not without
. The life of the plant. Plant physiology. 12 THE LIFE OF THE PLANT With the naked eye, or, better still, with the help of a lens, a small germ plant, a young shoot, consisting of a tiny stem with leaves and rootlet, is easily recognised (fig. i). This shoot binds together the two halves of the seed, which are called the cotyledons. These, though much larger than the Fig. I. shoot itself, are nothing but two appendages of it. But what is the nature of these cotyledons? Botanists say they are leaves. Those colourless, round, fleshy bodies, which remain underground are called leaves not without reason, as we shall immediately see. We have only to pass from a bean to its nearest relative—say the haricot—to find cotyledons appearing above the soil and becoming green like ordinary leaves (fig. 2). In the maple and the ash the cotyledons are still more like a common leaf, and the lime actually has small thin green leaves with well- marked veins and crenate outlines. Therefore the cotyledons of a bean, though they grow underground and are far from reminding us of actual leaves by their colouring or appearance, must be nevertheless regarded as such. Following upon those first organs, so unlike leaves, there appear, as the stem elongates, real leaves, though not yet of the shape we are accustomed to meet on a grown-up plant. Here is, for instance, a young ash plant. Everybody knows the shape of its leaf. Several pairs of leaflets are distributed on a common stalk with one leaflet more at the top. In this way a whole leaf consists of seven, nine, or more leaflets. This is called a compound leaf. What, then, do we notice here ? (fig. 3). The two fleshy, tongue-shaped cotjdedons are followed by two toothed leaves with prominent venation, which are simple, not compound, leaves. If we look further up the stem we shall notice other leaves composed of three leaflets, higher up. Please note that these images are extracted from scanned page images that may have been digitally enh
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Keywords: ., bookcentury1900, bookdecade1910, booksubjectplantph, bookyear1912
