Up Primary xylem Oak wood Leaf vein Vein ends Bean seed Pine tracheids, xs Fern TE, xs Fern, TE, mag Annular walls Annular, stretched Annular, narrow Scalariform walls Scalar., narrow CBP, pine CBP, dicot CBP, irregular Contact faces Pits, side view CBP, pine, xs CBP,angio, xs CBP, fern, xs Contact face, xs Simple perf. plate 1 Simple perf. plate 2 Pitted perf. plate Perf. plate & helix Perf. plate, face Perf. plate, mag Perf. plate, section Perf. plate rim Perf. plate & wall Scalariform Per plate Primary xylem Vessel sizes Fern TE Pine needle VE precursor, ls Protoxylem 9 Contact faces VE precursor, xs Precursor 2 Torn vessel Torn vessel 2
| |
Fig.
7.5-4b. Transverse section of a V-shaped vascular
bundle in a stem of asparagus (Asparagus). As in Fig. 7.5-4a, there are
two large cells here that are differentiating into vessel elements, but which
have not yet begun to deposit secondary wall. These too have been plasmolyzed by
the processes of fixation and dehydration. These cells are very large, but are
filled mostly with a large central vacuole rather than a large amount of
cytoplasm. Such large central vacuoles are very difficult to preserve well, and
they almost always collapse, as they did here.
|