An elementary text-book of botany / from the German of K. Prantl ; edited by S.H. Vines.

  • Prantl, K. (Karl), 1849-1893.
Date:
1889
Catalogue details

Licence: Public Domain Mark

Credit: An elementary text-book of botany / from the German of K. Prantl ; edited by S.H. Vines. Source: Wellcome Collection.

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    Only in comparatively few plants does a ligule occur; this is a small outgrowth from the npper (inner) surface of the leaf, tvliich is found in the Grasses at tho junction of the sheath and the blade (Fig. 8 A t), and also in the petals of many flowers, as Lychnis and Narcissas. In tho case of most leaves it is obvions that their internal tissnes are differentiated. The fundamental tissue, which is general ly green, the mesnpJnjü, is traversed by bright bands, which are the fibro-vaseular bundles or so-called veins. These usually project on the under surface, and when tho leaf decays, remain for a time as a slceleton of the leaf. The distribution of these bundles, the Fie. 8.—A Part of a leaf of Grass (Poa triviali») with the ligtilet; atlie hanlm; v the glienth; 1 lamina of the leaf. B Leaf of a Willow (Salix Caprta); astem; »s stipules; p petiole; / lamina; kaxillarybud (nat. gize). C X.eaf of a Pea (Pisum arvense); astem; <i gtipnles; rrachis; //leaflets; r/r/the npper leaflets motamorphosed into tendrilg; r'end of the rachis, likewigo transformed into a tendril. venaiion, is characteristic of large groups of plants. In the narrow leaves of most of the Monocotyledons the veins are parallel, branch- ing rarely or not at all (Fig. 13 L), and tliey are therefore said to be parallel-veined; whilo in many of the Dicotyledons only a few veins enter tho leaf, which branch frequently and anastomose, forming a rcticulated venation. According to the ramification of the veins, the venation may be either pinnate (Fig. 9 A), that is to say, a median vein or mid-rib runs through the leaf and gives off several lateral branches, as in the Tobacco, Beech, and Elm; or it may be palmate (Fig. 9 B), that is, the vein divides at its entrance into the lamina into a nnmber of equal diverging veins, which may again divide, as in the Maple and Ivy.