File:The structure and development of mosses and ferns (Archegoniatae) (1918) (14781897981).jpg

Identifier: structuredevelop00camp3 (find matches)
Title: The structure and development of mosses and ferns (Archegoniatae)
Year: 1918 (1910s)
Authors: Campbell, Douglas Houghton, 1859-1953
Subjects:
Publisher: New York, Macmillan
Contributing Library: The LuEsther T Mertz Library, the New York Botanical Garden
Digitizing Sponsor: The LuEsther T Mertz Library, the New York Botanical Garden

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h the symmetrical rhomboidalform of the cells of the young leaf is largely due (Fig. 90).The leaves do not retain their original three-ranked arrange-ment, but from the first extend more than one-third of the cir-cumference of the stem, So that their bases overlap, and theleaves become very crowded, and the two-fifth arrangement isestablished. The degree to which the central tissue of the stemis developed varies with the thickness of the branch. In themain stem it is large, but in the small terminal branches it ismuch less developed, as well as the cortex, which in these smallbranches is but one cell thick. Later the cortex of the largebranches becomes two-layered (Fig. 89, B), and is clearly sep-arated from the central tissue, whose cells in longitudinal sec-tion are very much larger. In such sections through the base V. MOSSES (MUSCI): SPHAGNALES—ANDREJEALES 171 of very young leaves characteristic glandular hairs are metwith. They consist of a short basal cell and an enlarged ter-
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minal cell containing a densely granular matter, which fromits behaviour with stains seems to be mucilaginous. The form 172 MOSSES AND FERNS chap. of the secreting cell is elongated oval (Fig. 89, D), and thehair is inserted close to the base of the leaf, upon its inner sur-face. The young leaf consists of perfectly uniform cells of anearly rhomboidal form (Fig. 90, A), and this continues untilthe apical growth ceases. Then there begins to appear the sep-aration into the chlorophyll-bearing and hyaline cells of themature leaf. This can be easily followed in the young leaf,where its base is still composed of similar cells, but wheretoward the apex the two sorts of cells become gradually differ-entiated. The future hyaline cells grow almost equally inlength and breadth, although the longitudinal growth some-what exceeds the lateral. These alternate regularly with thegreen cells, which grow almost exclusively in length, and forma network with rhomboidal meshes, whose interstices are occu

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