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 venation of the flower of Achlyphila is relatively simple in comparison with that of Abolboda. Fewer levels therefore suffice to show the principal features, and are shown in figures 82-87. The pedicel, illustrated in figure 82, contains two circles of bundles. The outermost of these circles departs into the bases of the three sepals (fig. 8:0, in such a way that five traces are present in each sepal (fig. 84). Successive levels (figs. 84, So) illustrate that above the level of sepal departure, the three whorls—petals, stamens, and gynoecium— become separate at approximately the same point. As in Abolboda, the stamen traces branch from the vein which can be demarcated as the midvein of each petal. No traces indicate any vestige of three other stamens, or of staminodia, which might be assumed to have been present primitively. About five traces are present in each petal, although these probably originate from about three traces in each petal base. The venation of the ovary is identical to that of Abolboda, as a higher level (fig. 8(i) indicates. As in Abolboda, widening of the petals is concomitant with branching of veins. Ridges, which fit into interstices between the sepals, were observed on the abaxial surface of the petals, and presence of these ridges alters the appearance of petal vascularization somewhat, for these ridges are vascularized. The venation of the style is as in Abolboda, except that no branching of the three veins takes place, as no appendages are present.

The similarities between Abolboda (e.g., A. linearifolia) and Achlyphila in respect to floral venation are quite striking. The only major differences are in the relative levels at which veins depart. Staminodia and ovary appendages are absent in Achlyphila, and three, rather than two, sepals are present (although some species of Abolboda also have three sepals).

FLORAL HISTOLOGY

Certain details of floral anatomy other than venation are worthy of description here because of their importance in suggesting specific and generic relationships. Some of these have been mentioned in connection wth sepal structure.

Corolla Lobe.

Corolla lobes, as might be expected, are thicker in their central portion than at their margins. The maximum width of corolla lobes was found to offer a convenient point of comparison. The corolla lobe of Abolboda linearifolia (fig. 92), like those of the other species of Abolboda, has a maximum width of approximately four mesophyll cells. The maximum mesophyll width in corolla lobes of Orcctanthe sceptnim subsp. occidental is (fig. 91) proved to be about 10 cell layers; these cells are much larger than those of Abolboda. In Achlyphila distich a, the maximum width (excluding ridges) appeared to be about 8 layers, as shown in figure 93, with a lignified sheath around veins.

Epidermal Relief.

In Abolboda, both corolla (fig. 92) and ovary exhibit epidermal relief. Such relief occurs on both surfaces of the corolla lobes. The formation is not merely a cuticular relief. The epidermal wall is raised into delicate, ridged eminences which run, predominantly, in a longitudinal direction on the organ concerned. These eminences are particularly prominent above radial walls of epidermal cells. The cuticle follows outlines of the epidermal cell-wall relief. Outlines of the cuticle, therefore, are parallel to those of the wall relief, but less detailed.

In Orcctanthe secpfnan subsp. Occidentalis (fig. 91), similar ridges were observed on the epidermis of corolla lobes, but they are much coarser and less detailed than those of Abolboda lincarifolia. On the ovary, virtually no relief occurs.

On petals of Achlyphihi disticha (fig. 93), no appreciable relief could be detected on epidermal cells. On the ovary, however, there are forms of epidermal cell relief which correspond closely with those of Abolboda linearifolia. Cuticular relief thus suggests similarity between the two genera.

Anthers.

The anthers in the three genera offer distinctive points of comparison. In Abolboda (e.g., A. lincarifolia, fig. 88), the connective is wide but thin. Between the veins and the anther sacs, the mesophyll of the connective is spongy. The endothecium is a single layer of cells wide. In Orcctanthe seeptrum subsp. Occident alis (fig. 89) the connective is rounded. The endothecium is a single layer of cells wide except at the portions of the anther sacs nearest the connective. The endothecial cells are large, and the thickening bands are narrow. The anthers of Achlyphihi (fig. 90) have a connective narrowed at their contact with the anther sacs. The connective itself is relatively narrow. The endothecium is a single of cells wide except where it is adjacent to the connective. Thickenings on endothecial cells are relatively wide compared with those of Orcctanthe and even Abolboda. Mention should be made of the conspicuous epidermal relief that occurs on the surfaces of the anther sacs. This feature offers a further point of comparison between Achlyphihi and other Xyridaceae.

Ovary Crests.

The ovary crests of Abolboda, a characteristic of that genus, consist of laru'e lignified cells. This is shown for A. sprncci in fig. 38.

Capsule Wall.

Mature capsule valves were available only in Aholhoda and Orcctanthe. As shown for .1. macrosiachya var. angustior (fig. 104) capsule valves in Abolboda consist of thick-walled sclerenchyma. Cells at the points where loculicidal dehiscence occurs are small and non-lignified. Likewise, the septa are not liffmfied, at least in their inner portions, and lignification is likewise absent where the valves are joined to the ovary base. The epidermal cells may be somewhat radially elongate, especially opposite the septa. Tn the fruits of Orectanthe (fig. 105) on the contrary, nullification even in mature fruits is mostly limited to the epidermal layer. (Vlls in this layer are mostly markedly elongate radially and sclerified.

Ovule.

Ovules of all species of Ab olio da for which appropriate stages were available showed the same features. The ovule is anatropous, with two integuments which are distinct from each other and the nucellus well back into the chalazal region. The integuments are each two cells wide. The megaspore mother cell is separated from the surface of the nucellus by a single layer of cells. The ovules of A. inacrostochi/a var. rob list ior showed some degree of wing formation, reminiscent of the condition in Orcctanthc. Ovules of Onctanthc were insufficiently well preserved to gain an accurate idea of their structure. They appear to be decidedly laterally flattened, however, so that a wing, composed on one side of the funiculus and on the other side, of the outer integument, is present. This wing is more than two cell layers in width, and this greater width extends to parts of the ovule other than the wing, as the several layers between epidermis and tanniferous layers in the seed shown in figure 103 indicate. An idea of the extent of the wing ean be gained from the figure of the seed of (). sccptrum given by Maguire, "Wurdack et al. (1958, fig. lm). The inner integument is not involved in wing formation.

The ovules of Achli/phila distich a- are identical in structure with those of Abolboda acicularis and other species which lack wings; in turn, these conform to the pattern described by AVeinzieher (1913) for Xyris indica.

Seed.

The seed of Abolboda is seemingly quite complex because of the four distinctive layer of cells. These four layers are shown in the longitudinal section (fig. 99) as well as the transection (fig. 100) and in the successive "paradermal" (tangential) sections shown in figures 94—97. The chalazal-micropylar axis is considered here as the longitudinal axis, and a sagittal section is considered a longitudinal section that passes through the funiculus and bisects the ovule.

The outermost layer of the seed is collapsed, or nearly so, at maturity. The cells are longitudinally elongate (fig. 94). These cells represent the relatively unmodified epidermis of the ovule. The cells of the hypodermal layer (fig. 9.1, excepting ridges) are large and highly vacuolate. They are enlarged in such a way as to occupy the valleculae of the wave-crest conformations of the layer beneath (see on fig. 100). The cells of the hypodermis are feAver than those of the epidermis, and are elongate laterally (fig. 95). They lack living contents at maturity. The two cell layers beneath the epidermis and hypodermis are distinctive in that (1) their walls are fairly thick and composed of a substance very refractory to staining, and (2) during their maturation stages, they first accumulate droplets of, then are entirely filled with a resin-like or tannin-like substance which stains bright red with safranin. The outer of these two layers (fig. 96) consists of cells that are tangentially elongate. In places, longitudinal ridges develop because of radial elongation of cells in this layer (fig. 100; tips of these ridges are seen in figure 95). These account for the longitudinal ridges seen in OTOSS aspect on seeds of Abolboda, as illustrated by Maguire, AVurdaek et al. (1958). The outer cell wall of each cell of this layer shows a relief, which consists of relatively large ridges. There is an adjustment, during maturation, so that cells of the hypodermis occupy spaces between the ridges, but are exceptionally thin atop the ridges.

The innermost layer (fig. 97) consists of more or less isodiametric cells, with contents as noted above. Cell layers internal to this layer (i.e., nucellar layers) are completely collapsed at maturity, and only a thin membrane of collapsed cell walls separates the endosperm from the innermost layer just mentioned. At the chalazal end of the ovule (fig. 98), the structure is altered. Instead of the four distinctive layers, numerous layers are present. These consist of cells like those of the innermost seed coat layer, with the same dense contents. They form a sort of operculum in the seed. In immature seeds, a number of nucellar layers which might be mistaken for a haustorium are present; during maturation stages, these collapse. The way in which the two layers with contents are altered at the micropyle is indicated in figure 101. The lumen of these cells is quite small in comparison with the thickness of the wall, and a two-layered wall condition is visible in the outer row of cells. Mention should be made of the fact that during maturation of the seed, walls of the cells with contents are obliterated, so that limits between these cells may be difficult to ascertain.