. Carnegie Institution of Washington publication. STRUCTURE. 33 two or three times as frequent, but somewhat more slender, and, though of nearly the same actual size, are much smaller in proportion to the size of the canals ; they are few in the root of N. flavo-virens, numerous in and N. odorata, very plentiful and of massive build in N. marliacea- chromatclla. Transverse sections show that they occur only in angles where three partition walls meet, and their arms project into the three adjoin- ing canals (Fig. 8). The canals vary in actual and rela- tive size in the different species
. Carnegie Institution of Washington publication. STRUCTURE. 33 two or three times as frequent, but somewhat more slender, and, though of nearly the same actual size, are much smaller in proportion to the size of the canals ; they are few in the root of N. flavo-virens, numerous in and N. odorata, very plentiful and of massive build in N. marliacea- chromatclla. Transverse sections show that they occur only in angles where three partition walls meet, and their arms project into the three adjoin- ing canals (Fig. 8). The canals vary in actual and rela- tive size in the different species, but are always largest at the middle of the medio-cortex and smaller toward exo- and endo-cortex. N. odorata (Fig. 8) has six or seven concentric rings of canals, i. e., that number can be counted along any radius of the root ; they are all quite large and distinct. N. tuberosa has seven to ten rows, very irregularly placed ; the middle and outer ones are approximately circular in outline, those near the endo-cortex are greatly elon- gated radially, and the innermost and outermost ones are scarcely more than large intercellular spaces. N. flava and N. lotus have six or seven rows of rounded and quite regular canals in the main part of the root, becoming irregular in N. lotus near the stem. N. marliacea- .. FIG. 9.— Contractile root of N. flavo-virens, trans- has nine rOWS, arranged verse section ; ; h, false epidermis ;. much as in N. tuberosa; the radial (-latei elongation of the inner canals causes the partition walls in this region to look like radial bead-like strings of cells. N. elegans X zanzibariensis has eight or nine rows of large canals, each of a rounded-hexagonal shape ; N . flavo-virens shows a similar structure in its nutritive roots. The cells of the partition walls are nearly square in side view (longitudinal section). The angles of the canals are occupied mostly by rounded-hexagonal cells ; three alternate sides of these face the canals, the o
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