THE GENUS SCHISTIDIUM (GRIMMIACEAE, MUSCI) IN HUNGARY ...

THE GENUS SCHISTIDIUM IN HUNGARY 53
H. H. Blom
(Figs 17, 18)
Plants medium-sized to large, forming mats or decumbent tufts. Central strand absent.
Hair-point 0.3–1.0 mm, erect, ± pellucid, hyaline but often brownish at insertion
(Fig. 17A, C), straight and stiff, terete, narrow throughout, not decurrent (the transition
between the hyaline and the chlorophyllose part of the apex smooth), distantly
spinulose-denticulate throughout. Costa and leaf margins smooth. Lamina smooth,
unistratose with bistratose patches in upper part. Lamina cells not or slightly sinuose, predominantly
isodiametric, in upper part 8–10 μm wide, in lower wider. K+ red.
Sporophytes common, immersed, but partly visible among the perichaetial leaves.
Urn straw-yellow to orange, becoming finely striolated when old, oval, widest at middle
(narrowed towards mouth), length/width ratio 1.6–2.0–2.4 (BLOM 1996), in Hungarian
material (1.4–)1.87 ±0.12(–2.5), n = 25. Exothecial cells predominantly elongate, 50–70 μm
long. Stomata 6–8 per urn (8–16 in subsp. wilsonii). Peristome teeth 350–430 μm long,
orange to red, entire or with narrow submarginal slits in central part, densely and coarsely
papillose, in lower part smooth or with papillae more distantly arranged.
S. elegantulum subsp. wilsonii (which has not yet been found in Hungary) differs
from the typical subspecies in a broader and coarser hair-point that appears rather whitish
(pellucid in subsp. elegantulum) and smooth (i.e. the spinulae are denser and smaller than
in subsp. elegantulum and not visible with a hand lens). Other differences include growth
form (dense tufts versus mats or decumbent tufts in subsp. elegantulum), hair-point length
in perichaetial leaves (up to 1.0–1.5 mm versus up to 0.7–0.9 mm), costa width at leaf base
(75–88 μm versus 53–78 μm), costa stratosity at leaf base (5–7 vs 4–5) and number of
stomata (8–16 vs 6–8).
In Hungarian plants of S. elegantulum, the hair-point appears smooth when viewed
in low magnification (as in subsp. wilsonii), due to few / short spinulae as seen in the compound
microscope. Otherwise, they possess the characteristics of subsp. elegantulum.
The differentiation between S. elegantulum and S. crassipilum can be very difficult in
Hungarian plants, although in other geographical regions (e.g. in Germany), S. elegantulum
poses no problems. Some plants could be considered transitional between the two
species, e.g. displaying sporophytes typical of S. elegantulum (oval urns with many stomata);
but leaves characteristic of S. crassipilum. The converse situation is observed as well. Such
plants have been placed in the latter, variable species during the present revision.
: S. elegantulum typically grows on ± shaded limestone or dolomite boulders
and rocks, sometimes on concrete; in Hungary it has rarely also been found on base-rich siliceous
rock (basalt, andesite). In Scandinavia, S. elegantulum subsp. wilsonii is reported to
grow on exposed to semi-shaded calcareous rocks, often on wall-tops.
Studia bot. hung. 39, 2008