YIP, KWOK LEUNG. University of Cincinnati Herbarium (CINC), Department of Biological Sciences, Cincinnati, Ohio 45221-0006; Current address: University Herbarium (UC), 1001 VLSB, University of California, Berkeley, CA 94720-2465. - A revision of the genus Pleuridium (Ditrichaceae, Musci).
The genus Pleuridium (Ditrichaceae) is revised on a worldwide
basis. Pleuridium species feature immersed, cleistocarpous,
basally stomatose capsules, cucullate calyptrae, and a paroicous or
autoicous sexual condition. Mostly ephemerals or annuals, the species
are widespread in the temperate regions and at higher elevations in
the tropics. Twenty-one species are classified in two sections:
Section Pleuridium includes P. ravenelii, P. acuminatum, P.
subulatum, P. papillosum, P. longirostre, P. arnoldii, P. curvisetum,
P. costesii, and P. pappeanum (9 species) while section
Sclerastomum includes P. nervosum, the designated type
species of the section, P. robinsonii, P. sullivantii, P.
mexicanum, P. laxirete, P. subnervosum, P. andinum, P. venezuelanum,
P. valetonii, P. denticulatum, P. sinensis, and P. holdridgei
(12 species). Two widespread, polymorphic, and morphologically
similar species, P. subulatum and P. acuminatum, have
caused much confusion since their inception. Correlations of sexual
condition and leaf lamina thickness with chromosome numbers show that
the two species are distinct.
Key words: embryophytes, monographic study, mosses, taxonomy