Organography of plants, especially of the archegoniatae and spermaphyta . have difterently. ^ Bower, op. cit., p. 600. DORSIVENTRAL LEAVES OF MONOCOTYLEDONES 323 2. MONOCOTYLEDONES. DORSIVENTRAL LEAVES. The simple construction and the predominance of intercalary growth inthe leaves of most Monocotyledones has been already mentioned \ but wemay here take as an illustration the formation of the leaf of Dactylisglomerata (Fig. 19H). Dactylis glomerata. The leaf is composed of a closed sheath anda lamina. At the point where these join is the membranous ligule. Thefunction of the leaf-sheath is to
Organography of plants, especially of the archegoniatae and spermaphyta . have difterently. ^ Bower, op. cit., p. 600. DORSIVENTRAL LEAVES OF MONOCOTYLEDONES 323 2. MONOCOTYLEDONES. DORSIVENTRAL LEAVES. The simple construction and the predominance of intercalary growth inthe leaves of most Monocotyledones has been already mentioned \ but wemay here take as an illustration the formation of the leaf of Dactylisglomerata (Fig. 19H). Dactylis glomerata. The leaf is composed of a closed sheath anda lamina. At the point where these join is the membranous ligule. Thefunction of the leaf-sheath is to support the internode which has longintercalary growth. If one holds horizontally the haulm of a grass which isstill in a condition of growth, and from which the leaf-sheath has beenremoved, it is unable to support its own weight. The ring-like swellingupon the leaf-sheath above its point of attachment may at first serve togive a firmer support to the haulm, because it is formed at the point wherethe tissue of the internode is softest. The importance of these nodes for. Fig. 208. Bambusa verticillata. Leaf in transverse section; I, hinge-cell. II, convolute lamina. Ill, hinge-cell after unfolding of leaf. All magnified. the erecting of the haulm is well known and need not be further spokenof here. The youngest primordium of a leaf on the massive vegetative cone has the formof a ridge which does not entirely surround the vegetative point. It is only in thesecond youngest leaf that the primordium takes on the form of a circular wall fromone side of which the lamina springs, and this side is marked out from the first bybeing somewhat higher than the adjacent part. This side grows more strongly,whilst the amplexicaul leaf-base, which at first is very small, develops by inter-calary growth gradually into the leaf-sheath. The laminar portion only appears assharply separated from the leaf-base after the appearance of the ligule. It is clearthat this development cannot be crisply inter
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