. The anatomy of woody plants. Botany -- Anatomy. FIG. 178.—Diagram of the lower region of the stem in Phylloglossum (after Bertrand). axis the fibrovascular tissues become so much reduced that internal phloem is no longer developed, and the continuity of the cylinder is interrupted by gaps which are not related to organs, but merely indicate the incom- plete development of the xylem . Where a trace is given off, as is shown in Fig. 179, it takes its origin opposite a strand and does not sub- tend an interval be- tween the bundles, clearly showing the lycopsid condition, even in the state of s
. The anatomy of woody plants. Botany -- Anatomy. FIG. 178.—Diagram of the lower region of the stem in Phylloglossum (after Bertrand). axis the fibrovascular tissues become so much reduced that internal phloem is no longer developed, and the continuity of the cylinder is interrupted by gaps which are not related to organs, but merely indicate the incom- plete development of the xylem . Where a trace is given off, as is shown in Fig. 179, it takes its origin opposite a strand and does not sub- tend an interval be- tween the bundles, clearly showing the lycopsid condition, even in the state of stelar reduction pre- sented in the evan- escent aerial axis. The Psilotaceae are anatomically distin- guished from the Lyco- podiaceae by the absence of true roots. Here the aerial stem, unless it be of very small size, is siphono- stelic in its organiza- tion. A thick-walled medulla is often pres- ent, but no internal phloem has been ob- served. The organiza- tion of the conducting tissues is radial and exarch; the leaf traces, as in Lycopodium, take their origin from the angles of the stele. In smaller aerial shoots and in the subterranean ones the central cylinder is usually protostelic. Sometimes gaps are present in the walls of the tubular cylinder of. FIG. 179.—Diagram of exit of leaf traces in the aerial stem of Phylloglossum (after Bertrand).. 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 resemble the original Jeffrey, Edward C. (Edward Charles), b. 1866. Chicago, Ill. , The University of Chicago Press
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