. Physiological botany; I. Outlines of the histology of phænogamous plants. II. Vegetable physiology. Plant physiology; Plant anatomy. STEMS OF MONOCOTYLEDONS AND DICOTYLEDONS. 129 the centre of the stem, and that the hard and thick vascular bundles, situated at the periphery of the stem, are older than the softer ones occupying the centre. For stems like those of Palms he used the term endor/enoics, giving the name exogenous to the other class, in which new layers are added to the outside of the wood. The terms endogenous and exogenous were adopted b3' De Candolle, and have played an importan
. Physiological botany; I. Outlines of the histology of phænogamous plants. II. Vegetable physiology. Plant physiology; Plant anatomy. STEMS OF MONOCOTYLEDONS AND DICOTYLEDONS. 129 the centre of the stem, and that the hard and thick vascular bundles, situated at the periphery of the stem, are older than the softer ones occupying the centre. For stems like those of Palms he used the term endor/enoics, giving the name exogenous to the other class, in which new layers are added to the outside of the wood. The terms endogenous and exogenous were adopted b3' De Candolle, and have played an important part in Systematic Botany. Comparative researches have shown that the term endogenous as applied to the growth of stems like those of Palms is not appropriate, and hence the correlative words have been generally abandoned as names of the two great groups of plants. They are now generally re- placed by tl)e words monocotj'- ledonous and dicotj'ledonous (see Vol. I. p. 69). Moreover, it is now gener- ally admitted that, although the distinctions pointed out in 366 — namely, those relating to the arrangement and course of the bundles — are valid for most plants of the two great groups, monocotyledons aud dicotyledons, they do not hold for all. 380. Instead of describing the numerous exceptions to both of these groups as ex- ceptions, many authors have endeavored to construct some new classification which shall embrace most of the anoma- lies in one or more co-ordinate divisions. Of these attempted tendrils is resumed. Every leaf has five fibro-vascular bundles, which are arranged unsymmeti'ically, as shown in the figure. The long distance through which some bundles can nm before uniting with any others, and the differences in structure at the successive nodes, are clearly exhibited in the diagram. Fig. 105. Diasramuiatic, projection of the disposition of tlie fibro-vascular bundles in Phaseolus vulgaris. This diagram, like Fig. 104, superposes two longitudinal sections, bot
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