Abolboda
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Authority
Carlquist, Sherwin J. 1960. Anatomy of Guayana Xyridaceae: Abutboda, Orectanthe and Achtyplola. Mem. New York Bot. Gard. 10: 63-117.
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Family
Xyridaceae
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Scientific Name
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Discussion
The flower of A. linear if olia (figs. 67-81) proved convenient material for a study of venation, and does not appear to differ appreciably from other species in these respects. The levels shown offer a series of selected sections from the base of the flower to the top. Because of venation complexities, a series of sections appeared preferable. The broken line in figures 67-69 is merely used to indicate incomplete separation of a sepal from tissue of the inflorescence receptacle at those levels.
At the lower level indicated (fig. 67) a vascular cylinder can be seen. The bundles of the cylinder have branched, at a level lower than that shown, to supply the approximately five traces present in each sepal. At the next level (fig. 68) sepal traces are in their characteristic positions, and divergence of median corolla bundles is indicated. Only ovary bundles are present on the central area a short distance above this level. Five traces depart to each third of the corolla tube; these thirds correspond to the three corolla lobes at a higher level. This is more evident in figure 69, which shows two of the three staminodia that will be alternate with these thirds of the corolla tube. There is a clearly definable midvein in each third of the corolla tube (see particularly figure 72). At the level shown in figure 60, as well as in figure 70. the nature of ovary venation is evident. There are three dorsal carpellary traces and three ventral ones, although the latter are fused together at these levels. At the next higher level (fig. 71) separation of the axial portion of the ovary into three placentas, each with a vein (or in some preparations, a pair of veins) is shown.
Figure 72 shows the termination of the ventral earpellary traces (below the level shown). The dorsal traces turn inward as the ovary narrows into the style, and only the three dorsal traces are present in the style base (fig. 73). In figure 73, the ovary appears fragmented into three portions (other than the style and style-appendages), and the larger triangular shapes represent the ovary crests. At the next level (fig. 74) departure of stamen traces, by branching from the median corolla traces, can be seen. The uppermost of the staminodia shown terminates at this level. In figure 75, the three corolla lobes become free from each other. Concomitantly with their greater widening into an imbricate conformation, there is considerable ramification of veins. The upper tips of two of the ovary crests may be seen at this level. The following figures show the changes in vaseularization of the style. In figure 76, departure of ovary appendages may be seen. These appendages are recurved, so that description of changes in their anatomy from departure to tip proceeds in the reverse order, in terms of figure numbers. The bundles that depart into the ovary appendages are branches of the three style traces, not the traces themselves. One of the appendages is very short; the other two (fig. 75) show an alteration in vaseularization. A cylindrical organization of the bundles is attained. At a lower level (fig. 74), these cylinders subdivide into several bundles, and at the tip of the appendages (fig. 73) only a single bundle is present. This bundle, in each, does not extend all the way to the appendage apex. Returning to the style proper (fig. 77), one may see that the three veins branch. This branching continues (figs. 78-81) so that numerous vein-endings enter the ultimate fringes of the stigma. Development of a central cavity in the style is illustrated in figure 80.
Variation in venation among the species of Abolboda seems to occur only in the number of bundles per sepal (see above) and the relatively abundant or few veins in the corolla, depending largely on corolla size. The question naturally arises, what interpretation of the ovary appendages seems most appropriate in terms of their venation, position, and histology. They cannot be regarded as equivalent to two of the three stigmas (if two are present), on account of their venation. They represent, rather, branches of the style bundles. The vein in each appendage does not terminate as a hydathode, nor do the contents of cells in the appendage suggest a nectary function, although this possibility should not be ruled out. The function of these structures —if they do have any prominent function—may well be related to a pollination mechanism in some way, but without further knowledge, speculations concerning function would be pointless. A feature of some interest is the nature of bundles in the very large ovary appendages of Oreetanihc. In 0. seeptrum, the bundle was observed to be large and rather diffuse, with isolated patches of xylem and phloem cells.
In respects other than numbers of veins and absence of staminodia, the. resemblance between Abolboda and Orrcimithc flowers are close, and ovary and style of Orectanthe flowers have a venation identical to that in Abolboda.