Monographs Details: Fissidens subbasilaris Hedw.
Synonyms:Dicranum subbasilare (Hedw.) D.Mohr, Skitophyllum subbasilare (Hedw.) Bach.Pyl., Schistophyllum subbasilare (Hedw.) Brid.
Description:Species Description - Plants usually dark green, often tinged with red. Stems monomorphic, curled inward when dry, to 12 mm [1.2 cm] long x 3.5 mm wide, unbranched and branched; rhizoids basal and axillary, smooth, reddish; axillary hyaline nodules absent; epidermis and outer 1-2 tiers of cortical cells small, incrassate, pigmented; inner cortical cells larger, hyaline; central strand present. Leaves rolled inward from tips when dry, usually imbricate, as many as 28 pairs, oblong, obtuse-apiculate to acute, to 2.4 mm long x 0.4 mm wide; margin evenly crenate-serrulate, but irregularly serrate distally, elimbate; costa distinct for part of its length, obscured distally by overlying bulging chlorophyllose cells, ending several cells below leaf apex, taxifolius type; dorsal lamina narrowed proximally, ending above or at insertion; vaginant laminae of cauline leaves 1/2-2/3 leaf length, acute, slightly unequal, minor lamina ending near margin; laminal cells obscure, eguttulate, irregularly bistratose, firm-walled, smooth, bulging, irregularly rounded-hexagonal, 7.5-10 µm long. Monoicous (cladauto-icous); perigonia terminal and axillary on stems and branches; perichaetia terminal on short axillary branches near proximal end of stem. Sporophytes not known in Neotropical plants. The following description is based on specimens from the United States. Sporophytes 1 per perichaetium, yellow-orange; seta smooth, 1.5-5.5 mm long; theca exserted, cylindric, erect, radially symmetric or nearly so, 1.8-2.0 mm long long; peristome teeth anomalous, finely papillose below, nearly smooth above; operculum conic, short-rostrate, 0.6-0.9 mm long. Spores finely papillose, 13-18 µm diam. Calyptra cucullate, smooth, ± 1.5 mm long, n = 8, 12 (Fritsch, 1991).
Discussion:Fissidens subbasilaris, endemic to North America, is distinguished by its short axillary perichaetial stems, elimbate leaves, irregularly serrate leaf apex, and short costa that is obscured distally by overlying, bulging, chlorophyllose cells. The only species in Mexico with which F. subbasilaris can be confused is F. obscurocostatus, but this species has a limbidium on the proximal half of perichaetial leaves and the sporophytes are terminal on long stems. Two species in South America, F. brevipes and F. cryptoneuron, also have a costa that is obscured, wholly or in part, by overlying, bulging, chlorophyllose cells. Both of these species, however, have pluripapillose laminal cells. Furthermore, the dorsal lamina in F. brevipes narrows abruptly to the insertion and the leaves are elimbate, while in F. cryptoneuron the costa is obscured its entire length, and a limbidium is restricted to the vaginant laminae of perichaetial and subtending leaves. The costa in two additional species, F. acacioides and F. gardneri, at times can be obscured by overlying chlorophyllous cells. Fissidens acacioides, however, is aquatic with usually much branched gametophytes and numerous axillary sporophytes with short setae so that the capsules are immersed to exserted. Plants of F. gardneri are very small, the laminal cells are pluripapillose, the costa does not extend much above the distal end of the vaginant laminae, and a limbidium is found on the proximal parts of perichaetial and 1-2 pairs of subtending leaves.
San Luis Potosí Mexico North America
| Tamaulipas Mexico North America