File:Text-book of structural and physiological botany (1877) (14776705635).jpg

Identifier: textbookofstruct00thom (find matches)
Title: Text-book of structural and physiological botany
Year: 1877 (1870s)
Authors: Thomé, Otto Wilhelm, 1840- Bennett, Alfred William, 1833-1902
Subjects: Plant physiology
Publisher: New York : J. Wiley & sons
Contributing Library: Smithsonian Libraries
Digitizing Sponsor: Biodiversity Heritage Library

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Fig. 443 II,—A peltate scale bearing the sporangia on its inner side facing the stem,five being visible (magnified); III. spore with the elaters unrolled which vi^erepreviously coiled spirally round it (greatly magnified) ; IV. E. JiMviatile; rhi-zome covered everywhere with root-hairs, and having four tubers about the size ofhazel-nuts which would, under favourable conditions, develope into new stems. dicotyledonous Casuarinese and the extinct Calamites, intheir mode of reproduction the Equisetaceae closely resembleFerns. In the internal structure of the stem the air-cavitiesare of great importance. Its centre is occupied by a largecentral air-cavity (Fig. 444 A, c) ; and in the surroundingring of tissue, which is often rather narrow, there is almostalways a cortical air-cavity (Fig. 444 A, r) between each
Text Appearing After Image:
Fig. 444. —A. Transverse section through the rhizome of Equisetum littorale: g vascular bundle surrounded by a sheath ; o central, r cortical air-cavities ( x 26)B. transverse section through a young stem of E. sylvaticuni ; o epidermisc collenchyma; r cortical parenchyma, many of the cells containing chlorophylls vascular bundle-sheath ; g vascular bundle ; l cortical air-cavity; lcentral air-cavity ; \J air-cavity of the vascular bundle ; st stoma (x 150). 320 Stricctural and Physiological Botany, pair of vascular bundles g. In addition, there often occuralso the so-called essential air-cavities (Fig. 444 B, l^) inthe vascular bundles. In some species the epidermis, whichconsists of a single layer of cells and is more or less stronglysilicified, has stomata (the Equiseta phaneropora ^); whilein others (Equiseta cryptopora), it is penetrated by crevicesbeneath which are the true stomata. The stomata (Fig. 444B, st) are always placed in a single or in several rows betweenthe elevate

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