Pylaisia species

Peristome and spore size variations in Pylaisia species with free endostomes ( Figs. 14–16 View Fig View Fig View Fig ).

Variation in peristome length and spore size was considered by Arikawa (2004) to be diagnostic for differentiation P. steerei from P. polyantha : endostome 380–500 µm mentioned in P. steerei vs. 300–380 µm in P. polyantha , and spores 15–18 µm vs. 11–14 µm corrrespondingly. Still somewhat indefinite understanding of these species forced us to discuss these quantative charactersists of Pylaisia with free endostomes in more details.

In most examined collections of P. polyantha from Russia spores were mainly 14–15 µm, occasionally 12 µm and 16 µm, and very rarely 10 and 17 µm, within the single capsules, mature but still operculate. In open capsules some spores were up to 20 µm, but as at the same time these capsules had at least few spores starting propagation (they also were enlarged to 20–22 µm in diameter); these measurements were ignored (such large spores usually slightly differ by more brownish color). Howev- er, in slightly immature capsules, although with separable operculum, spores about 8 µm only were sometimes observed. There are rather different data about the size of spores of P. polyantha in literature: 9.5–12.5 µm for Iberian Peninsula ( Gallego, 2018), 11–14 µm for the whole world ( Arikawa, 2004); 9–17 µm for eastern North America ( Crum & Anderson, 1981), 9–17(–20) µm for Mexico ( Sharp, 1994); 10–15 for Maine, USA ( Allen, 2014), 12–16 µm for Europe ( Limpricht, 1895), 11–17 for Netherlands ( Touw & Rubers, 1989); 13–16 µm for Great Britain and Ireland ( Smith, 2004), 13–18 µm for China ( Zhang & He, 2005). Comparing P. steerei with P. polyantha, Ando & Higuchi provided for the latter species spore size 12–16, rarely 18 µm.

Considering the variation within one capsule and published data, it is difficult to prove any differentiation, except the general tendency for Asian plants of P. polyantha ‘ orientalis ’ to have a slightly larger spores (14–15 µm prevailing in most capsules), whereas in Europe many collections have only few spores over 14 µm (although in more northern part of Europe and in the Caucasus spore size is more similar to plants from Asian Russia). The sequenced collections of P. steerei have spores mostly 14–16 µm, also e.g. Xinjiang specimen has spores 12– 14 µm, and several other falcate-leaved Pylaisia specimens from Russia have most spores less than 15 µm. Spore size variation in P. curviramea was identical to that in P. polyantha ‘ orientalis ’, and two genetically outlined entities, P. coreana and P. bezgodovii (described below), have spores smaller than 12 µm with solitary ones up to 13 µm in P. coreana .

Peristome length differentiation pattern in Russia is similar to that of spore size. Relatively short perisomes were observed in European P. polyantha and in P. coreana : exostome teeth to 200–250 µm long, and endostomes 250–300 µm long, while in P. curviramea , P. polyantha ‘ orientalis ’, and P. steerei exostome teeth were 250–300 µm long and endosotmes 300–380 (–400) µm long [e.g. in P. steerei from Xinjiang: 320–330 µm] ( Fig. 14 View Fig ).

More densely papillose endostome segments are usually observed in P. steerei ; it is better seen under SEM ( Fig. 15 G View Fig ), although light microscope is also sufficient for checking this character, cf. Fig. 14F View Fig , compare with Figs. 14D, E View Fig . The least papillose are endostomes in European and Caucasian P. polyantha ( Fig. 15 B, D View Fig ), and in P. coreana ( Fig. 14A View Fig ). In P. curviramea ornamentation of endostome is intermeriate between European P. polyantha and P. steerei : papillae are numerous but rather small and arranged at certain distance one from another ( Fig. 16 F View Fig ), not that densely as in P. steerei ( Fig. 15 G View Fig ). Endostome in P. polyantha ‘ orientalis ’ is similar to that in P. curviramea ( Fig. 14E View Fig ).

Exostome teeth on the dorsal surface are smooth below and papillose distally in all species with free endostome ( Fig. 15A, H View Fig ), and differences between species is not strong. Exostome teeth of P. steerei look more strongly papillose, which likely depends on more numerous dorsal trabeculae and larger size of papillae (cf. 15 C, F). In P. curviramea papillae in distal part of teeth on dorsal surface are not so numerous, but some of them are taller and under light microscope they form conspicuous projection from dorsal trabeculae (cf. Fig. 14D View Fig and 16 D View Fig ).