. The structure and development of mosses and ferns (Archegoniatae). Plant morphology; Mosses; Ferns. FILICINE^ LEPTOSPORANGIATM 331 tracheid (Fig. 184, B). In cross-section these bars are nearly rhomboidal, and give the famihar beaded appearance to sections of the tracheid wall. Sieve-tubes of very characteristic form are found in the bundles of all the Polypodiacese. In 0. strutliiopteris they occupy an irregular area at each end of the bundle. Their differentiation begins shortly after that of the large scalariform tracheids, and in some respects resembles it. The procambium cells from whic
. The structure and development of mosses and ferns (Archegoniatae). Plant morphology; Mosses; Ferns. FILICINE^ LEPTOSPORANGIATM 331 tracheid (Fig. 184, B). In cross-section these bars are nearly rhomboidal, and give the famihar beaded appearance to sections of the tracheid wall. Sieve-tubes of very characteristic form are found in the bundles of all the Polypodiacese. In 0. strutliiopteris they occupy an irregular area at each end of the bundle. Their differentiation begins shortly after that of the large scalariform tracheids, and in some respects resembles it. The procambium cells from which they arise are uniform in diameter, and have squarer ends than the young tracheids. Their contents are more colourless and finely granular than those of the tracheids, and the nucleus not so evident. The formation of the sieve- en. Fig. 183.—Woodwardia radicans. A, Part of a transverse section of a vascular bundle of the rhizome, X400 (about); B, transverse section of a root, X70; t, tracheids; s, sieve-tubes; en, endodermis. plates begins by transverse thickened bars on the lateral walls, less regular than in the tracheids, and the bars more or less anastomosing so as to enclose thin areas, the sieve-plates (Fig. 184, D, E). These occur all over the lateral walls, as well as the transverse ones. While it could not be positively shown, it is extremely probable that the pores, afterwards formed, pene- trate completely the thin membrane of the sieve-plates, and throw the adjacent sieve-tubes into communication. While it is usually supposed that there are no nuclei in the adult sieve-tubes, in several instances, evidences of the presence of a number of small nuclei were met with. A further inves- tigation of this point is desirable. With the tracheary tissue is mingled more or less wood-. Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance of these illustrations may not perfectly
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