Plagiochila incerta Gottsche

Gradstein, S. Robbert & Reeb, Catherine, 2022, The genus Plagiochila (Dumort.) Dumort. (Marchantiophyta) in Madagascar, Cryptogamie, Bryologie 20 (5), pp. 65-106 : 79-80

Plagiochila incerta Gottsche

( Fig. 8 )

Plagiochila incerta Gottsche, Annales des Sciences naturelles, Botanique (sér. 4) 8: 324 (1857). — Type: Mauritius. Commerson 33 (lecto-, designated here, PC0100688!; isolecto-, G00064456!).

Plagiochila crollii Steph. , Bulletin de l’Herbier Boissier (sér. 2) 4(4): 356 (1904).— Type: Madagascar. 18.XI.1900, Croll s.n. (lecto-, designated by Grolle [1995], G00045461!).

Plagiochila nemophila Gottsche, Abhandlungen des Naturwissenschaftlichen Vereins zu Bremen 7: 339 (1882).— Type: Madagascar. “Silva Amabaranavaranututa”, 6.XII.1877, Rutenberg s.n. (lecto-, designated by Grolle [1995], G00128913!).

Plagiochila boivinii sensu Vanden Berghen (1981) , non typus (fide Grolle 1995).

ADDITIONAL SPECIMENS EXAMINED. — Madagascar. NE Madagascar, Pervillé s.n. (PC). — Prov. Antananarivo • Mandraka Forest Reserve, II.1974, Onraedt 74M 2172, 74M 2174, 74M 2175, det. Vanden Berghen as P. boivinii (BR) ; I.1959, Bosser 12580, det. Vanden Berghen as P. boivinii (BR) . — Prov. Antsiranana • Marojejy Reserve, Andampibe valley, III.1990, Pócs 90112/J p.p. (EGR). — Prov. Fianarantsoa • Vohiparara, III.1978, Tixier 11543, det. Vanden Berghen as P. boivinii (BR) ; Ranomafana Nat. Park, Sahamalaotra Forest near Vohipara village, VII.2004, Pócs et al. 04120/BU (EGR); Namorona river waterfalls, Pócs 04126/CS (EGR, GOET); slope of Mt. Vatolampy near Ambatolahy village, Pócs 04129/G (EGR); 1016 m, on pole, IX.2017, Reeb17M619 (PC). — Prov. Toamasina • Masoala Peninsula W coast, summit ridge S of Amanizana village, among Thysananthus spathulistipus, IX.1994 , Pócs 9449/I (EGR, GOET); Nosy Mangabe Island, Pócs 9450/S (EGR); Andasibe-Mantadia Nat. Park, III.1990, Pócs et al. 90103/S, 90105/g, 90106/ AA, 90106/P (EGR); ridge of Mt. Andrianavibe, Pócs 9487/BR, 9487/BX (EGR).

DISTRIBUTION AND HABITAT. — East African Islands ( Comores, Madagascar, La Réunion, Mauritius). In Madagascar found on bark in lowland and lower montane forests, from sea level to 1250 m. On La Réunion found at low elevation, 200-300 m ( Vanden Berghen 1981).

DESCRIPTION (see also Vanden Berghen 1981 as P. boivinii ) Plants 2.5-6 mm wide, to 8 cm long, flaccid, dichotomous or slightly and irregularly pinnate, branches usually intercalary, occasionally terminal, rhizome-like creeping shoot present. Mature stem leaves imbricate, widely and horizontally spreading, asymmetrically ovate-rectangular to narrowly ovate-triangular, 1.7-2× longer than wide, widest at the base, unbordered, ventral bases ampliate and forming a low crest, apex usually bifid, ventral margin plane or slighly undulate at the base, apex usually bifid, with two lobe-like teeth up to ten cells long and usually a smaller tooth in the middle, ventral margin toothed over almost its whole length with 10-20 narrowly triangular to linear teeth, the teeth 2-5(-10) cells long, made up of subrectangular cells; dorsal base long and broadly decurrent, covering part of the stem and made up of mostly short cells (rarely elongate), ventral bases shortly to rather longly and narrowly decurrent, the decurrent linear portion 0.1-0.4 mm long, entire. Leaf cells subisodiametrical, 20-35 µm wide in midleaf, with conspicuous but not or only slightly swollen trigones, leaf base without vitta-like area, cells in the dorsal leaf base not elongate; cuticle smooth; oil bodies not observed. Underleaves absent. Androecia terminal. short, of 4-6 pairs of bracts. Perianth without stalk, perianth mouth densely laciniate. Vegetative reproduction not observed.

NOTES

Plagiochila incerta (sect. Vagae) is recognized by the rather robust plants with ampliate, horizontally spreading and regularly imbricate, ovate-triangular leaves with a toothed and sometimes bifid apex, toothed ventral margin and entire or toothed ventral base, entire and longly and broadly decurrent dorsal leaf bases, and leaf cells with conspicuous but not strongly swollen trigones. Branching is terminal and intercalary. Plagiochila incerta may be confused with P. repanda var. perrotana and P. kiaeri , but P. repanda var. perrotana has leaves with smaller cells and large, swollen trigones and an ill-defined border of thicker-walled cells, whereas P. kiaeri differs by ventrad leaves with smaller cells and dorsal leaf bases with elongate cells.

Vanden Berghen (1981) provided a detailed description and illustrations of P. incerta under the name P. boivinii Steph. The type of P. boivinii , however, has non-ampliate leaves and small trigones, and is close to P. africana Steph. and P. neckeroidea Mitt. (see also Jones 1962). The confusion was apparently caused by the isolectotype material of P. boivinii (G00065447), which consists of a mixture of P. boivinii and P. incerta ( Grolle 1995: 112) . Our study of material in BR identified by Vanden Berghen as P. boivinii confirms that the material belongs to P. incerta .

Vanden Berghen (1981) suggested a close relationship between P. incerta (as ” P. boivinii ”) and the neotropical P. montagnei , but the latter species has underleaves (absent in P. incerta ) and frequent vegetative reproduction by propagula from leaf surfaces (not observed in P. incerta ). Moreover, the leaves in P. montagnei are more ovate-rectangular in shsape and the leaf cells are smaller, 16-25 µm wide in midleaf, with small trigones ( Heinrichs & Gradstein 2000).

Figures

FIG. 8. ― Plagiochila incerta Steph.: A, habit; B, shoot in ventral view with terminal female branch; C, shoot in dorsal view with intercalary branching; D, leaves; E, portion of leaf margin; F, G, leaf apex; H, I, midleaf cells. From Reeb CR17M619 (PC, TAN). Scale bars: A, 5 mm; B-D, 1 mm; E, 0.25 mm; F, G, 0.1 mm; H, I, 0.05 mm.