File:The structure and development of mosses and ferns (Archegoniatae) (1918) (14598336758).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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margin is occupiedby a number of growing points formed by the rapid dichotomyof the original apex, and separated only by a few rows of cells.From the lower side of the thallus grow numerous rhizoidsof the thin-walled form. The whole upper surface is cov-ered with the sexual organs, each of which is surrounded byits own very completely developed envelope. A vertical section passing through one of the growingpoints (Fig. 30, C) shows a structure closely like a similarsection of Riccia. The apical cell (x) produces dorsal and 1^ MOSSES AND FERNS CHAP. ventral segments, and from the outer cells of the former thesexual organs arise exactly as in Riccia. On the ventral sur-face the characteristic scales of Riccia are absent, and are re-placed by the glandular hairs found in most of the anacrogy-nous Jungermanniales. The development of the archegonium shows one or twopeculiarities in which it differs from other Hepaticse. Themother cell is much elongated, and the first division wall, by c $
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Fig. 30.—Sphcerocarpus Californicus (?). A, Male plant, X40; ^, antheridia; B,median section of a similar plant, X80; C, the apex of the same section, X240;h, ventral hair. which the archegonium itself is separated from the stalk, issome distance above the level of the adjacent cells of thethallus, so that the upper cell is very much smaller than thelower one. The upper cell has much denser contents than thelower one, which instead of remaining undivided as in Riccia,divides into two nearly equal superimposed cells, this division Ill THE JUNGERMANNIALES 77 taking place about the same time as the first division in thearchegonial cell (Fig. 31, B). The divisions in the latter arethe same as in Riccia, and the general structure of the arche-gonium offers no noteworthy peculiarities. The number ofneck canal cells is small, probably never exceeding four, and inthis respect recalls again Riccia. The central cell is relativelylarge, and the ventral canal cell often nearly as large as theQg

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