Plagiochila pectinata Lindenb.

Gradstein, S. Robbert & Reeb, Catherine, 2022, The genus Plagiochila (Dumort.) Dumort. (Marchantiophyta) in Madagascar, Cryptogamie, Bryologie 20 (5), pp. 65-106 : 86

Plagiochila pectinata Lindenb.

( Fig. 12 )

Plagiochila pectinata Lindenb. , Species Hepathicarum (fasc. 1): 14 (1839). — Type: Mauritius. Unknown collector (holo-, W; fide Grolle 1995).

SPECIMENS EXAMINED. — Madagascar. Prov. Antananarivo • Ankaratra, Manjakatompo Forest Reserve, VIII.1971, Cremers 1713, 1734 ( BR); IX.1994, Pócs 9481/ AK, 9481/ N ( EGR, GOET); Tavolotara Forest Reserve , XII.2017, Reeb 17 M904 ( PC). — Prov. Antsiranana • Marojejy Nat. Park, XI.1972, Guillaumet 4077, 4080 ( BR); ridge N of Andampibe Falls, III.1990, Pócs et al. 90113/CQ, 90113/ CT, 90113/ P ( EGR); elfin forest on ridge, Pócs 90114/AN, 90114/ BG ( EGR).— Prov. Fianarantsoa • Analabé near Ambositra ,

VIII.1971, Onraedt 71M5232, 71.M5236 (BR); Nosiarivo, X.1976, Tixier 9464, 9465 (BR); Andringitra Nat. Park, tributary W of Korokoro river, IX.1994, Pócs 9473/AY (EGR, GOET); foot of Mt. Vohipia, Pócs 9477/AN (EGR); Ranomafana Nat. Park, ridge of Mt. Vohipanani, VII.2004, Pócs 04121/DN (EGR); summit ridge Mt. Vatolampy, Pócs 04128/G (EGR).

DISTRIBUTION AND HABITAT. — Widespread in tropical and southern Africa. In Madagascar commonly found on bark, rock, soil and rotten wood in subhumid to humid mid-elevation and montane forests, 700-2150 m.

DESCRIPTION (see also Jones 1962; Vanden Berghen 1981) Plants 3-5 mm wide, to 5 cm long, very flaccid, irregularly pinnate, branches intercalary, rhizome-like creeping shoot present. Mature stem leaves distant to contiguous, obliquely to widely spreading, somewhat ventrad, sometimes curved backwards, symmetrically or asymmetrically oblong-ligulate, c. 2-3× longer than wide, widest in the middle, often caducous, base not ampliate and not shouldered, leaves with 2-8 small to rather long triangular teeth at the apex and along the upper half of the ventral margin, the teeth 2-5- 8) cells long, largest at the apex, made up of subquadrate cells, dorsal margin and leaf bases entire; leaf bases shortly and narrowly decurrent, decurrent ventral part c. 0.2 mm long. Leaf cells subrectangular, 20-30 µm wide in midleaf, 1.3-2× longer than wide, with conspicuous trigones, the trigones radiate on the longer cell walls and becoming confluent, margin cells sometimes thicker-walled and forming an obscure border; leaf base without vitta-like area; cuticle smooth; oil bodies not observed. Underleaves absent. Androecia slender, terminal to intercalary, with 3-15 pairs of bracts, the bracts dorsally overlapping, ventrally not overlapping. Perianth obovate-oblong to subcylindrical, enveloped by bracts, not stalked, perianth mounth toothed by numerous coarse triangular teeth. Vegetative reproduction by caducous leaves.

NOTES

Plagiochila pectinata (sect. Heteromallae) is recognized by the wide-spreading, somewhat ventrad, narrowly oblong leaves, which are c. 2-3× as long as wide and toothed only in the upper part, and absence of terminal branches. The leaf cells are (sub)rectangular, 1.3-2× longer than wide, and sometimes thicker-walled along the leaf margin, forming an obscure border. Plagiochila pectinata may be confused with P. terebrans but the latter species has terminal branching and less strongly ventrad leaves, and the leaves are not caducous. Plagiochila pectinata approaches the neotropical P. gymnocalycina and P. simplex , but the leaves in the latter two species are less widely spreading and usually more strongly asymmetrical, with the ventral margin more widely arched outwards. Moreover, the leaf cells in P. gymnocalycina and P. simplex are less elongate, the leaf margins are not bordered by thicker-walled cells, and the perianth is elevated on a short stalk. In P. pectinata the perianth is not stalked. In P. simplex , moreover, the stem leaves are less than 2× longer than wide (more than 2× longer than wide in P. pectinata and P. gymnocalycina ).

Figures

FIG. 12. ― Plagiochila pectinata Lindenb.: A, habit; B, shoot in dorsal view; C, shoot in dorsal view; D, shoot in ventral view; E, intercalary branching; F, branch leaves; G, stem leaf; H, leaf margin showing teeth; I, midleaf cells; J, perianth. From Tixier 9462, 9474 (PC). Scale bars: A, 5 mm; B-D, F, G, 1 mm; E, I, 0.5 mm; J, H, 0.25 mm.