Morton, Conrad V. & Lellinger, David B. 1966. The Polypodiaceae subfamily Asplenioideae in Venezuela. Mem. New York Bot. Gard. 15: 1-49.
Aspleniaceae
Genus Description - The genus Asplenium, known in English as "spleenwort." in French as "doradille," and in Spanish as "doradilla," is rather readily recognizable by a combination of characters - often rather small size, thin texture, veins usually free and ending far short of the margin, often in hydathodes visible from the upper surface, sori dorsal on the veins and elongate, and indusia conspicuous and persistent. elongate, generally membranous, generally glabrous and entire, directed proximally, and covering the sporangia while young. One of the most characteristic features are the rhizome scales (and blade scales where they exist, although they are not abundant in most species) which are "clathrate, that is to say like a window with numerous small panes of clear colorless glass, the result of the scale cells being large and broad, with dark lateral walls and colorless exterior walls. However, some rhizome scales in some species of Asplenium do have the central part of the scales dark, due both to the thickening of the lateral walls with a consequently smaller lumen, and to the coloration of the exterior walls: such scales are here described as "bicolorous." although they are never so strikingly so as in some species of Cheilanthes, Bleehnum. and other genera. The scales are usually quite entire, but since the marginal wall of the marginal cells is usually colorless, the dark top and bottom walls of the marginal cells appear to protrude and appear to be teeth or cilia except under high magnification. The rhizome scales strongly suggest those of the genus Vittaria. One species (A. squamosum) is anomalous in having the scales conspicuously fimbriate-lacerate, the elongate teeth being several cells broad at the base.
Many species of Asplenium strongly resemble species of Diplazium, and as a matter of fact all of Diplazium was included in Asplenium by Mettenius and other noted pteridologists. Actually, although it runs through a very similar series of variations, Diplazium may not be very closely allied at all, and it is here excluded from the subfamily. It has sometimes so-called diplazioid sori; that is, there are indusia placed back to back along the same veins, one directed proximally and one distally. However, only a few sori on any frond ever show this character (these mostly the basal ones) and some species seem never or hardly ever to have diplazioid sori. The presence of even one diplazioid sorus is an indication of a plant belonging to Diplazium rather than Asplenium, although we cannot swear that diplazioid sori never occur in Asplenium. In Diplazium, the rhizome scales are described as "fibrous" rather than "clathrate," by which is meant that the cells are usually much more elongate, with a consequently relatively narrow lumen in comparison with the lateral walls, which show up as a series of more or less elongate "fibers." Also, the outer walls are frequently colored brownish, which tends to give them an over-all darker color than those of Asplenium, which are almost always beautifully iridescent from the clear glassyappearing outer walls. Another character, considered by some as a decisive one, is that in Asplenium the stipes have two somewhat lunate-shaped steles at the base, which approach each other toward the middle or apex of the stipe and join at their middles to form an X-shaped single stele, which persists throughout the rhachis of the blade. In Diplazium the two steles join at one end, and thus form a single U-shaped stele at the top of the stipe and in the rhachis. This distinction appears to be true, but one must say that so few species have actually been investigated in this respect that the matter is far from certain. The chromosome numbers are different, basically 36 in Asplenium and 41 in Diplazium, in which it differs from Athyrium (n = 40), with which it has been united by Copeland. Diplazium generally (or always) has some septate hairs present on the blades, whereas Asplenium is commonly entirely glabrous. That this is not a fundamental character is shown by A. pumilum, which has blades definitely septate-hirsute, and some other species that are more or less hairy. Extremely minute, almost microscopic, hairs occur on the blades of several species.
Geographic distribution: Of the 47 species treated, 20 occur in the Guayana Highlands region, but most of them rather locally, so far as information is currently available. Within the Guayana Highlands area, two (A. harpeodes, A. praemorsum) are known from Mount Roraima only, one (A. pediculariifolium) from Tafelberg (Suriname) only, three from the Sierra de la Macarena, Meta only (A. falcinellum, A. laetum, A. macarenianum, the latter endemic), one from the Vaupes region only (A. spruceanum), two from Suriname and British Guiana only (A. auriculatum, A. salicifolium), three from Amazonas and Bolivar (Venezuela) only (A. cristalum, A. radicans, A. serra); the remaining nine species are more widely distributed within the Highlands region (A. angustum, A. auritum, A. cunealum, A. formosum, A. juglandifolium, A. pferopus, A. rutaceum, A. serratum, A. zamiifolium).
Many of the remaining Venezuelan species are quite local, some of them having been collected in only one state. They seem to be concentrated in the Distrito Federal and the states of Aragua and Merida, but this perhaps only reflects the activities of some botanists who have collected most actively in these regions, especially of Moritz and Fendler (in the vicinity of Colonia Tovar, Aragua), and of Funck and Schlim and Linden in Merida. Six species are apparently confined to the high Andes in the state of Merida (A. castaneum, A. cladolepton, A. fragile, A. palmeri, A. repandulum, A. resiliens).
In the following treatment all specimens are in the U. S. National Herbarium unless otherwise indicated. Photograph numbers cited refer to the negative number of photographs taken by the senior author. A full set of photographs is in the U. S. National Herbarium, and duplicates have been widely distributed.