Hygrohypnum

Authority

Hedenäs, Lars. 2003. Amblystegiaceae. Fl. Neotrop. Monogr. 89: 1--107. (Published by NYBG Press)

Family

Campyliaceae

Scientific Name

Hygrohypnum

Synonyms

Hygrohypnum palustre Loeske, Hygrohypnum luridum (Hedw.) Jenn.

Description

Genus Description - Plants medium-sized, sometimes small (outside the area large); green, yellow, or brown (outside the area rarely with clear red colors). Stem soft or somewhat stiff, pinnately or irregularly branched in one plane, sometimes sparsely branched; central strand usually present (rarely absent); hyalodermis absent; pseudoparaphyllia foliose (outside the area outer ones sometimes filamentose); paraphyllia absent; rhizoids smooth (outside the area sometimes weakly warty-papillose), usually slightly to moderately strongly branched, inserted at or just below costa insertions; axillary hairs with 1-4 (outside the area to 9) upper, hyaline (outside the area sometimes early yellowish or brownish) cells. Stem leaves erect to erect-patent (outside the area sometimes spreading), straight or falcate (gradually curved); ovate or oblong-ovate, narrowing gradually or abruptly to acuminate to acute or sometimes obtuse apex (outside the area sometimes oblong or broadly ovate to almost orbicular with a broadly obtuse apex), not plicate, concave (outside the area sometimes plane), decurrent or not; margin slightly recurved near base, otherwise plane (outside the area sometimes recurved almost throughout), denticulate or finely so in upper part; costa single and long, or shorter if forked or double; median laminal cells linear or short-linear, unistratose, ± incrassate and eporose or indistinctly porose, smooth (outside the area sometimes distally prorate); alar cells differentiated (outside the area sometimes undifferentiated), quadrate to short-linear and often inflated or slightly inflated in lower group, transverse-rectangular to short-rectangular in upper group; alar group indistinctly or well delimited, quadrate to rectangular, along basal margin of leaf (outside the area sometimes triangular). Branch leaves similar to stem leaves or smaller; proximal branch leaves ovate or broadly ovate to almost orbicular, obtuse or with rounded or occasionally apiculate apex. Autoicous (outside the area dioicous). Perigonial leaves narrowing abruptly from broad base to obtuse to short-acuminate apex. Inner perichaetial leaves narrowing gradually or abruptly to acute or acuminate apex, mostly plicate; margin unbordered or indistinctly bordered, denticulate or strongly denticulate in acumen, denticulate or dentate at shoulder; costa varying from single and long to double and short; vaginula with paraphyses. Calyptra naked. Seta long, reddish; capsule cylindrical or short-cylindrical and curved or slightly curved throughout, horizontal or almost so; annulus separating or rarely persistent; operculum conical. Exostome well developed; teeth cross-striolate below, papillose above, dentate or slightly dentate above. Endostome well developed, with high basal membrane; segments not or narrow-perforate along midline; cilia 0-3(-4), as long as segments (outside the area sometimes somewhat shorter), nodose. Spores 10.5-24.0 µm, finely papillose to almost smooth.

Discussion

Note. Before the study of Jamieson (1976), the genus Hygrohypnum was circumscribed to include various, partly unrelated species that have evolved adaptations to growth in running water. Many of the earlier included species belong to the Brachytheciaceae (especially Platyhypnidium), tropical Hypnaceae, or Sematophyllaceae (cf. the excluded taxa at the end of this treatment). Even with the narrower circumscription of Jamieson (1976), the genus is unlikely to be monophyletic. To achieve a better treatment, Hygrohypnum needs to be split, and the various species groups now included in the genus need to be compared with other Amblystegiaceae and probably temperate Hypnaceae taxa. The single species occurring in the neotropical area is the type of the genus.

Distribution

Hygrohypnum includes approximately sixteen species (Jamieson, 1976), mainly distributed in the northern temperate to arctic areas. One species occurs also at higher altitudes in tropical areas of SE Asia and S America.

Asia| South America|