BFNA Title: Hamatocaulis
Author: L. Hedenäs
Date: Sept. 2000
Edit Level: R
Version: 3

Bryophyte Flora of North America, Provisional Publication
Buffalo Museum of Science
1020 Humboldt Parkway
Buffalo, NY 14211 USA


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Hamatocaulis - Calliergonaceae

Edit Level R


XX. HAMATOCAULIS Hedenäs, Lindbergia 15: 27. 1989 [1990] * [Latin hamatus, hooked, and caulis, stem]

Lars Hedenäs


Plants medium-sized to very robust, sometimes turgid, green, brownish, variegated green and red, or entirely red or brownish to blackish red. Stem pinnately or irregularly branched ± in one plane, with shoot apex often hooked, without central strand and without hyalodermis, cells inside cortex thin-walled; pseudoparaphyllia broad, rare; rhizoids or rhizoid initials on stem at or just before the leaf nerve insertion; axillary hairs with 2--6 distal hyaline cells. Stem leaves from ± erect or patent base usually suddenly curved in distal portion, ovate to broadly ovate, with acute or acuminate apex, near apex often suddenly narrowed to short-apiculus, usually distinctly plicate, concave or strongly so; margin often finely but irregularly denticulate near leaf apex, otherwise entire; costa single, ending in distal half of leaf; median lamina cells thin-walled or slightly incrassate, eporose or porose; alar cells not differentiated from other basal cells, not or hardly decurrent. Sexual condition dioicous; inner perichaetial leaves plicate; vaginula with paraphyses. Capsule curved and ± horizontal; annulus separating; exostome externally basally reticulate, margin slightly dentate distally. Spores 10.5--24.5  \um.


The species of Hamatocaulis are characterized by lack of a central strand or hyalodermis, thin and relatively poorly developed cortex, undifferentiated alar cells, and plicate and from an erect base suddenly suddenly curved leaves. The last feature is found also in Scorpidium. Hamatocaulis is one of the genera of the Calliergonaceae where red pigments are frequently present in at least parts of the plants. When only parts of the leaves are red, the pigment is mainly found in a subbasal transverse band. Hamatocaulis species are found in mineral-rich to intermediately mineral-rich, but usually not in calcium-rich habitats that are often slightly nutrient-enriched.


Species 2 (but see below; 2 in the flora): Holarctic region, but with scattered occurrences farther south.


SELECTED REFERENCES: Hedenäs, L. 1989. The genera Scorpidium and Hamatocaulis, gen. nov., in Northern Europe. Lindbergia 15: 8--36. Hedenäs, L. and P. Eldenäs. 2007. Cryptic speciation, habitat differentiation, and geography in Hamatocaulis vernicosus (Calliergonaceae, Bryophyta). Pl. Syst. Evol. 268: 131--145. Janssens, J. A. 1983. Past and extant distribution of Drepanocladus in North America, with notes on the differentiation of fossil fragments. J. Hattori Bot. Lab. 54: 251--298. Wynne, F. E. 1944. Studies in Drepanocladus. IV. Taxonomy. Bryologist 47: 147--189.



1. Stem leaf base ± erect (and often ± appressed to the stem) or slightly spreading, ovate and not or slightly constricted at insertion; stem leaves ca. 0.6--1.1 mm wide . . . 1. Hamatocaulis vernicosus


1. Stem leaf base ± patent, broadly ovate and distinctly constricted at insertion; stem leaves ca. 0.8--2 mm wide . . . 2. Hamatocaulis lapponicus



1. Hamatocaulis vernicosus (Mitten) Hedenäs, Lindbergia 15: 27. 1989 [1990]


Stereodon vernicosum Mitten, J. Linn. Soc. Bot. 8: 43. 1864; Drepanocladus vernicosus (Mitten) Warnstorf


Plants medium-sized to almost robust, not turgid, mostly ± pinnately branched; shoot apex often hooked like a walking stick, green, brownish or variegated green and red, rarely almost entirely red. Stem leaves with ± erect base, ovate, ca. 0.6--1.1 mm wide, slightly narrowed at leaf insertion, apex shortly or longly acuminate, concave, strongly or less commonly slightly plicate, often with red transverse sub-basal zone, more rarely larger parts of leaf red.


Mineral-rich, though usually not calcium-rich, and often slightly nutrient-enriched, spring-influenced habitats, or on lake shores; 0--1400 m; Alta., B.C., Man., N.W.T., Ont., P.E.I., Que., Yukon; Alaska, Conn., Ill., Ind., Maine, Mich., Minn., N.J., N.Y., Ohio, Oreg., Vt., Wash.; West Indies (Dominican Republic), South America (Colombia, Venezuela), Eurasia, (Africa?).


Hamatocaulis vernicosus is widely distributed but rarely common, seemingly rare or lacking in the Arctic, in the northern-central parts of the continent, and in the most oceanic areas. It is usually easily recognized by the distinctly plicate stem leaves having erect bases and suddenly curved upper parts. The stem leaves lack differentiated alar cells and the stem lacks central strand and hyalodermis. Molecular studies have revealed that H. vernicosus consists of two cryptic species in Europe. So far, all molecularly studied North American material (from Minnesota) belongs to one of these, but since the other one is known from South America this could well occur in North America as well. Much material originally filed under H. vernicosus in herbaria examined belonged to other species, mainly to Scorpidium cossonii, Sanionia uncinata and Palustriella falcata, and almost all earlier Drepanocladus s.l. species have been confused with this species.


2. Hamatocaulis lapponicus (Norrlin) Hedenäs, Lindbergia 15: 30. 1989 [1990]


Hypnum lycopodioides var. lapponica Norrlin, Not. Saelsk. F. Fl. Fenn. 13: 293. 1873; Drepanocladus lapponicus (Norrlin) Smirnova


Plants robust to very robust, occasionally smaller, turgid, mostly sparsely and irregularly branched, shoot apex sometimes hooked, variegated red and green, brownish red or blackish red, more rarely green throughout. Stem leaves with patent base, broadly ovate, ca. 0.8--2 mm wide, distinctly constricted at leaf insertion, apex acute or acuminate, concave or strongly concave, plicate or almost smooth, often with red color present in large parts of leaf, sometimes only in transverse, sub-basal zone.


Wet, mesotrophic and often spring-influenced mires or on lake shores, sometimes submerged in lakes; 0--1050 m; Alta., Yukon, Alaska; n Eurasia.


Hamatocaulis lapponicus is rare in the western parts of the continent. It is recognized by its large size (approximately as large as Scorpidium scorpioides), usually slightly plicate stem leaves without differentiated alar cells, and stem with neither central strand nor hyalodermis. Besides the larger size, H. lapponicus differs from H. vernicosus in its ± patent stem leaf bases, and in stem leaves broadly ovate and more distinctly constricted at their insertion. Hamatocaulis lapponicus is usually also more sparsely and irregularly branched than H. vernicosus, has somewhat less plicate leaves than the latter, and large parts of its shoots are more often red than is the case in the latter.