Monographs Details: Achlyphila
Authority: Carlquist, Sherwin. 1960. Anatomy of Guayana Xyridaceae: Abutboda, Orectanthe and Achtyplola. Mem. New York Bot. Gard. 10: 63-117.
Family:Xyridaceae
Scientific Name:Achlyphila
Discussion:

The markedly flattened inflorescence axis of this genus (fig. 44) suggested that more or less prominent differences from Abolboda would be present. In fact, despite the obvious differences in shape, the similarities are perceptible. To be sure, the epidermis (which is two-layered in places at the edges of the axis) is heavily sclerified. Then, too, bundles (each with a fibrous sheath) occur in the cortical region on each edge of the axis. Aside from these differences, one can cite similarities in the ehlorenehyma: two layers of palisade and several spongy layers are present. Adjacent to the outer margin of the sclerenchyma ring—or "ellipse"—bundles are present, each sheathed by a single layer of fibers along the outer surface, as in Abolboda. Bundles are present in the sclerenchyma, toward the inner margins of its extent. The central ground tissue consists of thin-walled parenchyma and (unlike Abolboda, but like Xyris) contains no bundles. The last-cited feature suggests that the resemblances of Achlyphila may lie closer to Xyris than to Abolboda.

Because Achlyphila is unique among Xyridacrac in not having a congested inflorescence, elongate pedicels are present. As is shown in figure 82, the pedicel is triangular in outline. Like the inflorescence axis, the pedicel has a sclerified epidermis. Two circles of bundles, one adjacent to the inner margin of the sclerenchyma ring (or, at lower levels, just within the ring) may be found. A central zone of thin-walled parenchyma is present.

Discussion.

The above descriptions must not be construed as exhibiting the full range of variation either in a species or in an individual axis, although an attempt is made to suggest the nature of such variation. Because of this variability, species characters are difficult to offer. The inflorescence stems of Abolboda macrostachya are distinctive on account of their greater size (with more numerous bundles). Special features in the axes of A. amerkmia (a single circle of "pith" bundles; collapsed parenchyma pockets) and A. ciliata (1-2 circles of "pith" bundles; prominent protoxylem lacunae in these) may be noted. The extent of sclerenchyma seems roughly correlated, in Abolboda, with size of the axis, and the sclerenchyma ring in A. macro at achy a is much wider than in A. amerkana. Likewise, the very wide sclerenchyma cylinder in Orrctanthe may be correlated with the large diameter of that axis. The selerified epidermis, the lack of concentric arrangement of bundles, the presence of scattered bundles in the cortical region, and the presence ou these of fibrous sheaths are all characters which differ to a certain extent from comparable conditions in Abolboda, and enforce the generic status of Orcctanthe. The descriptions of Achlyphila above have shown that inflorescence-axis anatomy serves both to distinguish this genus generically, and to relate the genus to other Xyridaceae, probably to Xyris most closely.

Vessels.

Solereder and Meyer (1929) cite a report of vessels with simple perforation plates in inflorescence axes of Xyris carolitviana, X. indica, and X. laccra. In the present study, such vessel elements were observed in longitudinal sections of inflorescence axes of the following taxa: Abolboda acicularis, A. americana, A. macrostachya var. macrostachya, A. macrostachya var. robustior, and Orectanthe sceptrum. Cheadle (1942) indicates vessels with simple perforation plates in Xyris flexuosa and X. smalliana.

INFLORESCENCE BRACTS

One or more bracts tend to occur along the inflorescence axis, and several are associated with the congested inflorescence itself. The former are here termed inflorescence-axis bracts and the latter inflorescence bracts. These bracts show patterns of structure different from those of sepals or leaves, and are worthy of description. In some instances {Abolboda acicularis, A. ciliata) the difference between structure of inflorescence-axis bracts and sepals is not very great. Because inflorescence-axis bracts and inflorescence bracts vary in structure from base to apex, and even within a plant, depending on their position, their structure is difficult to categorize accurately in all instances. Sections studied are discussed by species.