Weissia newcomeri (E.B. Bartram) K. Saito, J. Hattori Bot. Lab.

Weissia newcomeri (E.B. Bartram) K. Saito, J. Hattori Bot. Lab. View in CoL 39: 423. 1975. — Bryologist 50: 162. f. f– h. 1947. Fig. 4 View Fig .

Plants in small, more or less dense patches, green or yellowish-green. Stems 1–5(–10) mm long. Leaves contorted and incurved or crisped when dry, erect-spreading to spreading when wet, 1.4–2.5× 0.3–0.45 mm, lanceolate or oblong, with length/width ratio 4–6(8):1, with upper leaf margins narrowly and weakly incurved, slightly cucullate at apices, lower leaves with hardly widened bases, upper leaves with slightly widened bases; costa 40–60 (–90) µm wide at base, excurrent into short, smooth mucro, smooth dorsally, ventral stereid band 1–2-layered, dorsal stereid band 2–3-layered, dorsal epidermis not or slightly differentiated; upper and mid-leaf cells quadrate and rounded-hexagonal, thin- or moderately thick-walled, 6–9×7–11 µm, papillae 3–4(–5) per cell, low, simple and bifid; basal leaf cells rectangular, smooth, yellowish, with moderately thickened walls, 20–50×8–12 µm. Autoicous. Perichaetial leaves similar to upper stem leaves, with slightly wider bases. Setae (4–) 5–6 mm, yellowish, later becoming light-brownish. Urns ca. 1 mm long, cylindrical, weakly narrowed to mouth. Exothecial cells thin-walled. Annuli differentiated, opercula falling off, low conic and with narrow, straight or oblique beaks ca. 0.5 mm long. Peristome absent. Spores (15–)18–21 µm.

Distribution and ecology. Until recently, this species was considered to be an endemic of Japan, were it is distributed in Honshu, Kyushu, Sikoku, and Okinawa. In Russia it occurs in the southern Far East (Amurskaya Province, Khabarovsk and Primorsky Territories), and in one locality in Kamchatka (Klyuchevskie volcanoes). It grows in forests on soil banks on slopes, along roads and streams, and on rocks and cliffs.

Differentiation. Leaves with obtuse apices and weakly, narrowly incurved upper margins make this species similar to W. planifolia , but the latter species is readily distinguished by having a well developed peristome. Oth- er eperistomate species of Weissia with long setae occurring in Russia are W. condensa (Voit) Lindb. and W. brachycarpa (Nees & Hornsch.) Jur. The former species has leaves with stronger involute margins and stronger costae; its distribution in Russia is restricted to the European part. Weissia brachycarpa also has stronger incurved leaf margins, shorter setae, and urns clearly narrowed to the mouths.

KEY TO IDENTIFICATION OF WEISSIA SPECIES OCCURRING IN RUSSIA 1

1. Upper and median leaf cells bulging on both surfaces, with 1–2 high, strongly branched papillae per cell ........................................................... W. armata View in CoL

— Upper and median leaf cells not bulging or slightly bulging only on ventral surface, with 3–5 low, simple and bifid papillae per cell ............................... 2

2. Setae shorter than urns, capsules immersed into perichaetial leaves...................................................... 3

— Setae as long as urns or longer, capsules emergent or exserted above perichaetial leaves ................... 6

3. Annuli not differentiated ...................................... 4

— Annuli differentiated, consisting of few rows of small cells; opercula persistent or falling off ................. 5

1 – The key includes W. wilsonii View in CoL and W. angustifolia View in CoL based on their circumscriptions of Callaghan et al. (2019). Few specimens from Russia studied by us appeared to be not genetically similar to so-called specimens from outside Russia. However, our data are so far too few for certain conclusion, hence we call for attention of collectors from Russia to plants with such features.

4. Capsules round, obtuse, abruptly narrowed into short beaks .................................................. W. longifolia View in CoL

— Capsules short ellipsoidal, gradually narrowed into low conic, strait or oblique beaks ......... W. wilsonii View in CoL

5. Perichaetial leaves with almost flat or weakly incurved upper margins; opercula often fall off in nature ........................................................... W. levieri

— Perichaetial leaves with strongly involute upper margins; opercula usually do not fall off in nature ....... ........................................................ W. angustifolia View in CoL

6(2). Capsules on long setae; opercula fall off easily; peristome present, well developed or short .................. 7

— Capsules on short or long setae; opercula fall off easily or can be removed only with special effort; peristome absent ......................................................... 10

7. Anteridia naked, in leaf axils close to archegonia; peristome usually short, occasionally strongly reduced ............................................... W. wimmeriana View in CoL

— Perigonia bud-like, on stems below perichaetia; peristome well developed ............................................. 8

8. Upper leaf margins almost flat or weakly incurved; peristome teeth reddish-brown, erect to slightly reclined when dry ................................. W. planifolia View in CoL

— Upper leaf margins tightly incurved; peristome teeth pale reddish or yellowish, erect when dry ............ 9

9. Upper leaf margins widely incurved; spores 15–20 µm; widespread .. W. controversa var. controversa View in CoL

— Upper leaf margins narrowly incurved; spores (19–) 21–25 µm; Russian Far East ................................... ........................... W. controversa var. sachalinensis View in CoL

10(6). Setae 1–3 mm long; capsules cleistocarpous or with differentiated annulus but with opercula persistent in nature ....................................................... 11

— Setae 3–8 mm long; capsules stegocarpous ........ 14

11. Setae as long as urn; capsules emergent ................. ............................................................. W. rostellata View in CoL

— Setae 2–3 times longer than urns; capsules exserted 12

12. Perichaetial leaves with tightly involute upper margins; spores 16–21 µm .......................... W. exserta

— Perichaetial leaves with weakly incurved upper margins; spores 20–25 µm ....................................... 13

13. Setae straight; opercula falling off, but epiphragm remaining at mouth, so spores are released through breaks of capsule walls ...................... W. squarrosa

— Setae arcuate when wet; opercula differentiated but persistent, not falling off in mature capsules .......... ................ W. cf. exserta (cf. Fedosov et al., 2023.)

14(10). Leaf margins plane or weakly incurved in distal portion; urns hardy narrowed to the mouths .......... .......................................................... W. newcomeri

— Upper leaf margins widely and tightly involute; urns narrowed to the mouths ....................................... 15

15. Spores 14–16(–20) µm; costae 60–80(–100) µm wide ............................................................ W. condensa

— Spores 16–24 µm; costae 30–50 µm wide .............. ........................................................ W. brachycarpa