Systematic Anatomy of the Dicotyledons; A Handbook for Laboratories of Pure and Applied Botany Volume 1 (Paperback)

This historic book may have numerous typos and missing text. Purchasers can download a free scanned copy of the original book (without typos) from the publisher. Not indexed. Not illustrated. 1908 edition. Excerpt: ...solitary crystals, sphaerites and crystal-sand; the latter either occupies the lumen (Cotyledon, Sedum), or is embedded in the membrane (Crassula, Rochea, Sempervivum) of the cell. Tannin is frequently present in the Order, and is occasionally stored up in special cells, which are distinguished either by their small size or by their development as long sacs; in the leaf the latter are found, especially in the epidermis or in the subepidermal layer of cells. As regards the structure of the axis, the secondary vessels, which are always enclosed in unlignified tissue, have simple perforations and simple-pitted walls; the wood-prosenchyma bears simple pits. The appearance of the xylem in transverse section varies, inasmuch as the thin-walled groups of tissue, together with the secondary vessels and the wood-prosenchyma, may or may not be present, and inasmuch as both may be concerned to a varying extent in the formation of the xylem. Medullary rays are rarely developed. Where cork occurs, its formation takes place in a superficial layer of cells. The following features also require special mention: the occurrence of cortical vascular bundles in species of Rochea, Sedum and Sempervivum, the remarkable stemstructure of Sedum populifolium, Pall., and the anomalous root-structure of Sedum maximum, Sut. 2. Structure Of The Leaf. The leaf-structure is, as a rule, centric or intermediate between bifacial and centric in structure. Typical palisade-tissue is only rarely present. As a rule the stomata occur on both sides of the leaf. They are usually surrounded by subsidiary cells, exhibiting a characteristic arrangement (Fig. 70, A). For the stomata arise by divisions, resembling those of an apical cell; by successive walls, arranged in three directions, as...