Hookeriopsis

• Authority

  Buck, William R. 1998. Pleurocarpous mosses of the West Indies. Mem. New York Bot. Gard. 82: 1-400.

• Family

  Pilotrichaceae

• Scientific Name

  Hookeriopsis

• Description

  Genus Description - Plants small to medium-sized, in lustrous, yellow-green or more often golden and bronze-tinged, often dense mats. Stems creeping, red, freely but irregularly branched, branch apices usually cuspidate, evenly foliate, not or scarcely complanate-foliate; in cross-section without a hyalodermis, with a few rows of small thick-walled cells surrounding several large thin- or firm-walled cells, central strand none; rhizoids tufted on lower surfaces of bases of stems, finely roughened; pseudoparaphyllia filamentous or small and folióse but branches mostly arising in leaf axils; axillary hairs 2-celled, with a short brown basal cell and an elongate hyaline distal cell. Leaves crowded, usually homomallous to falcate-secund, scarcely altered when dry, lanceolate to ovate-lanceolate, gradually acuminate, concave with channelled acumina, shortly rounded to the insertion; margins not bordered, subentire to serrulate above, entire below, plane or narrowly incurved; costa double, diverging throughout, ending at or usually below midleaf, sometimes absent, not projecting at apex; cells long-hexagonal to linear, smooth, thin- to firm-walled, the walls narrower than the lumina, ± porose, ± homogeneous throughout leaf, not becoming larger toward the insertion except in a few rows at extreme base, there broader, shorter, and colored; alar cells not differentiated. Asexual propagula sometimes present in leaf axils. Dioicous. Perichaetia ± inconspicuous, on older portions of stems; leaves ± erect, with spreading apices, lanceolate, gradually long-acuminate, similar to vegetative leaves but usually ecostate and with laxer basal cells. Setae elongate, smooth throughout, reddish, curved at extreme apex; capsules horizontal to pendent, cylindric; exothecial cells subquadrate to short-rectangular, collenchymatous; annulus not differentiated; operculum rostrate from a conic base; columella broadly cylindric, V2 as long as the urn or shorter; peristome double, attached at the mouth, exostome teeth narrowly triangular, bordered, ± shouldered at 2/3-3/4 the length of the teeth, on the front surface usually with a median furrow, the plates cross-striolate below shoulder, smooth to coarsely papillose above it, ± trabeculate at back, smooth to finely papillose; endostome smooth to finely papillose, with a high basal membrane, segments keeled, not perforate, with baffle-like crosswalls, cilia none. Spores spherical, smooth to finely papillose, fairly small. Calyptrae mitrate, lobed at base, naked or with a few hairs, smooth.

• Discussion

  Hookeriopsis (Besch.) A. Jaeger, Ber. Thatigk. St. Gallischen Naturwiss. Ges. 1875-76: 358. 1877; Hookeria sect. Hookeriopsis Besch., Ann. Sci. Nat. Bot. VI, 3: 240. 1876. Discussion. Hookeriopsis was described by Bescherelle (1876) to include only the two species treated here. Although the concept of Hookeriopsis has een greatly expanded since then, I am recognizing it in the strict, Bescherellean sense. As such, the genus is characterized by lanceolate or ovate-anceolate, concave leaves with channelled apices. The most striking feature is the relatively short, double costa, ending below midleaf. The areolation is omogeneous except for a row or two of cells along the insertion. The seta is smooth throughout and the exothecial cells are collenchymatous. The propagula in one of the species are an interesting feature and unique in the alliance. Hookeriopsis is probably most closely related to Brymela. In both genera a hyalodermis is not differentiated, the leaves are not bordered and only serrulate above, and the leaves are rounded to the insertion. Significantly, the areolation is homogeneous throughout the leaf. The two genera are separated by size and development of the costa. They seem particularly related in light of species such as B. websteri, which is similar to H. luteo rufescens except or its larger size, incrassate leaf cells, and much stronger costa. Hookeriopsis is close to Trachyxiphium but differs in the much smaller, noninflated marginal teeth on smoothly concave rather than ± plicate leaves. Also, in Trachyxiphium the leaf apices are longer and the costa is not only longer but usually strongly projects along much of its upper portions. Thamniopsis is very different from Hookeriopsis and probably closest in relationship to Trachyxiphium. It has in common with that genus strongly serrate leaf margins, often with inflated teeth, and strong, projecting costae. Thamniopsis differs significantly from Hookeriopsis, Brymela, and usually Trachyxiphium in the stem hyalodermis, the bordered leaves, and the heterogeneous laminal areolation in which the basal portion of the leaves has much laxer cells than the upper part. Although these generic segregations are somewhat tentative, they are based on examination of approximately 3/4 of all Hookeriopsis s.l. species, from the Americas, Africa, and Asia.