BFNA Title: Scorpidium
Author: L. Hedenäs 
Date: February 6, 2008
Edit Level: R
Version: 4 08206

Bryophyte Flora of North America, Provisional Publication
Missouri Botanical Garden

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Calliergonaceae - Scorpidium


XX. SCORPIDIUM (Schimper) Limpricht, Laubm. Deutschl. 3: 570. 1899 * [Latin scorpio, alluding to shoot apex like a scorpion tail]


Lars Hedenäs

Hypnum subg. Scorpidium Schimper, Syn. 650. 1860; Limprichtia Loeske.


Plants medium-sized to very robust, sometimes turgid, green, brownish yellow, brownish to blackish red or red. Stem irregularly to pinnately branched ± in one plane, with weak central strand (rarely lacking) and at least a partial outer hyalodermis, cells inside cortex thin-walled; pseudoparaphyllia broad; rhizoids or rhizoid initials on stem at or just before leaf insertions; axillary hairs with 2--9(--11) distal hyaline cells. Stem leaves from erecto-patent base suddenly curved in distal portion, sometimes indistinctly so or ± straight, ovate-lanceolate to broadly ovate (sometimes almost orbicular), with obtuse, apiculate, acute or acuminate apex, not or hardly plicate, concave or strongly concave; margin finely denticulate or ± entire near leaf apex, entire proximally; costa either long and single, ending in distal half of leaf, or short and single or double (rarely absent); median lamina cells thin-walled to strongly incrassate, eporose to porose; differentiated alar cells 2--20, shortly to longly rectangular, thin-walled and hyaline, strongly inflated, in small transversely triangular group, not or hardly decurrent. Sexual condition  dioicous or autoicous; inner perichaetial leaves plicate; vaginula with paraphyses. Capsule curved and ± horizontal; annulus separating; exostome reticulate or partly (rarely entirely) basally cross-striolate externally, margin slightly dentate distally. Spores 12--21 \um.


Scorpidium species are characterized by a hyalodermis of inflated, thin-walled epidermis cells, which is present in at least part of the stem circumference. Unlike Hamatocaulis species, they have at least a weak central strand in the stem, except in very weak plants. They have small alar groups consisting of a few (2--20) inflated and thin-walled cells that are sharply delimited from the surrounding cells. Their stem leaves are normally smooth and, like those of Hamatocaulis, from an erect base suddenly curved above, except in most expressions of S. scorpioides. Although S. scorpioides superficially looks very different from the other two members of the genus, these differences are mainly found in characters, such as size and leaf shape, that affect the appearance of the plant to the naked eye. On the other hand, molecular evidence and critical microscopic features of, e.g., stems, alar cells, and exostomes relate this species to S. cossonii and S. revolvens. Based on molecular evidence, Scorpidium scorpioides is an ingroup within S. cossonii, and is thus an example of a species with a number of autapomorphies that are easily visible to the naked eye, in a genus where the two other members have a more generalized appearance. Scorpidium species are found in mineral-rich to intermediately mineral-rich and normally nutrient-poor habitats. When mineral-rich these habitats are mostly rich in calcium.


Species 3 (3 in the flora): widely distributed in the Holarctic region, with scattered occurrences in more southern areas (also in the southern hemisphere).


SELECTED REFERENCES Hedenäs, L. 1989. The genera Scorpidium and Hamatocaulis, gen. nov., in Northern Europe. Lindbergia 15: 8--36. Hedenäs, L. and P. Eldenäs, P. 2008. Relationships in Scorpidium (Calliergonaceae, Bryophyta), especially between S. cossonii and S scorpioides. Taxon 57: 121--130. 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. Kooijman, A. & Hedenäs, L. 1991. Differentiation in habitat requirements within the genus Scorpidium, especially between S. revolvens and S. cossonii. J. Bryol. 16: 619--627. Wynne, F. E. 1944. Studies in Drepanocladus. IV. Taxonomy. Bryologist 47: 147--189.



1. Stem leaves strongly concave, almost orbicular and obtuse to apiculate, or from broadly ovate to broadly ovate-lanceolate base narrowed to apiculate, acute or acuminate point, falcate or (rarely) straight; costa usually double, more rarely single or lacking, rarely reaching above mid-leaf; hyalodermis of stem often incomplete; stem leaves ca. (0.7--)1--2.4 mm wide . . . 3. Scorpidium scorpioides


1. Stem leaves concave, from ovate to ovate-lanceolate base narrowed to shortly to longly acuminate apex, falcate; costa single, ending in upper half of leaf; hyalodermis of stem complete; stem leaves ca. 0.5--1.1 mm wide.


2. Autoicous; mid-leaf cells 61--140(--179) \um, with shortly to longly fusiform-narrowed cell ends; outer peristomial layer usually predominantly (more than 40--50%) cross-striolate basally . . .       1. Scorpidium revolvens


2. Dioicous; mid-leaf cells of stem leaves 14--95(--120) \um, with square to shortly fusiform-narrowed cell ends; outer peristomial layer of exostome predominantly (more than 70%) dotted basally. . . . 2. Scorpidium cossonii


1. Scorpidium revolvens (Swartz ex Anonymo) Rubers in A. Touw & W. V. Rubers, De Nederlandse Bladmossen 380. 1989


Hypnum revolvens Swartz ex Anonymo, Monthl. Rev. 34: 538. 1801; Drepanocladus revolvens (Swartz ex Anonymo) Warnstorf; D. revolvens var. miquelonensis (Renauld & Cardot) Grout; Limprichtia revolvens (Swartz ex Anonymo) Loeske


Plants medium-sized to robust (sometimes when submerged), not turgid, shoot apex not hooked, green, red, purplish red, dark brownish red or blackish red. Stems sparsely and irregularly or more rarely ± pinnately branched, with well-developed, complete hyalodermis. Stem leaves from erecto-patent or patent base ± suddenly curved distally, ovate or ovate-lanceolate, gradually narrowed to acuminate or longly acuminate apex, sometimes near apex suddenly narrowed to apiculus, ca. 0.5--1 mm wide, concave; costa single, ending in distal half of leaf; median lamina cells (shorter half of leaf) 61--140(--179) \um, cell ends shortly or longly fusiform-narrowed (rarely rounded to almost square), differentiated alar cells 2--10. Sexual condition autoicous. Peristome: proximal outside of exostome predominantly (more than 40--50%) cross-striolate basally.


More or less common except in regions with strongly calcium-rich soils or bedrock in the boreal and Arctic zones, farther south mainly in mountainous areas, intermediately mineral-rich and often spring-influenced fens, small periodically water-filled depressions, shores or, more rarely, submerged; 0-3020 m; Greenland; St. Pierre and Miquelon (Miquelon); Alta., B.C., Nfld., Man., N.W.T., Nunavut, Ont., Que., Sask., Yukon, Alaska, Colo., Idaho, Mich., Minn., Mont., Ohio, Vt., Wis., Wyo.; South America; Eurasia (including Papua New Guinea); s Africa, Pacific Islands (New Zealand); Antarctic.


This species has often been confused with S. cossonii, and the differences between these species are discussed under the latter.


2. Scorpidium cossonii (Schimper) Hedenäs, Lindbergia 15: 18. 1989 [1990]


Hypnum cossonii Schimper, Musci Eur. Nov. Bryol. Eur. Suppl. fasc. 3--4 (Mon.): 5, 5. 1866; Limprichtia cossonii (Schimper) L. E. Anderson, H. A. Crum & W. R. Buck; Drepanocladus intermedius (Lindberg) Warnstorf; D. revolvens subsp. intermedius (Lindberg) Grout; D. revolvens var. intermedius (Lindberg) L. R. Wilson


Plants medium-sized to robust (sometimes when submerged), rarely slender, not turgid, shoot apex sometimes slightly hooked, green, yellow-green, brown or brown-red. Stems pinnately or sometimes irregularly branched, with well-developed, complete hyalodermis. Stem leaves from erecto-patent or patent base ± suddenly curved distally, ovate or rather broadly ovate, gradually narrowed to shortly or longly acuminate apex, near apex often suddenly narrowed to apiculus, ca. 0.5--1.1 mm wide, concave; costa single, ending in upper half of leaf; median lamina cells (shorter half of leaf) 14--95(--120) \um long, cell ends square, rounded or shortly fusiformly narrowed, differentiated alar cells 2--10(--15). Sexual condition dioicous. Peristome: lower exostome outside predominantly (more than 70%) dotted basally.


Common in regions with calcium-rich soils or bedrock in the boreal and Arctic zones, farther south mainly in mountainous areas, ± calcium-rich habitats in fens, springs, periodically water-filled depressions, shores or, more rarely, submerged; 0-3650 m; Greenland; Alta., B.C., Man., Nfld., N.W.T., Nunavut, N.S., Ont., Que., Sask., Yukon; Alaska, Colo., Conn., Ill., Iowa, Maine, Mich., Minn., Mont., N.J., N.Y., Ohio, Vt., Wis.; South America, Eurasia, Pacific Islands (New Zealand).


Scorpidium cossonii is often confused with S. revolvens or Hamatocaulis vernicosus. From the latter it is easily separated by its hyalodermis and the usually present central strand of the stem, and by its differentiated hyaline and inflated alar cells of the stem leaves. Hamatocaulis vernicosus, which lacks all these features, usually has distinctly plicate stem leaves, whereas these are smooth in S. cossonii. Scorpidium cossonii differs from S. revolvens in being dioicous (the latter is autoicous) and in having shorter mid-leaf cells in the stem leaves. The ends of these cells are square to shortly fusiform-narrowed in the first species whereas they are shortly to longly fusiform-narrowed in the latter. Both species may have red or strongly red colors, and in such cases S. cossonii is usually brownish red while S. revolvens is mostly blackish or purplish red. Due to a large variation in both species, especially when herbarium material is also considered, color should, however, be used with care in identifying specimens. Dark purplish plants usually belong to S. revolvens and predominantly green or yellow-green plants with a brown-red costa or costa and leaf base belong to S. cossonii. The differences in leaf areolation between the two species make S. cossonii less glossy than S. revolvens, but this character, like the difference in size and branching pattern (S. cossonii is slightly smaller and more richly and regularly branched than S. revolvens), which is obvious in mixed collections, is often difficult to use in identification without much experience. In mixed collections S. cossonii has more shortly acuminate stem leaves than S. revolvens, but both species are variable in this character and the overlap between them is great.


3. Scorpidium scorpioides (Hedwig) Limpricht, Laubm. Deutschl. 3: 571. 1899


Hypnum scorpioides Hedwig, Sp. Musc., 295. 1801


Plants robust or very robust, occasionally medium-sized, turgid plants, often with a characteristic claw-like shoot apex, green, brown or often red to blackish red. Stems mostly sparsely or irregularly pinnately branched, with partial or complete hyalodermis (more than 25% of stem circumference). Stem leaves from erecto-patent to patent base usually rather suddenly curved distally, rarely straight or almost so, varying in shape from almost orbicular to broadly ovate-lanceolate, suddenly narrowed to obtuse and mostly apiculate point or more gradually narrowed to acute or acuminate point, ca. (0.7--)1--2.4 mm wide, strongly concave; costa double or occasionally single (rarely absent), reaching somewhere below to very rarely slightly beyond middle of leaf, when single often branched; median lamina cells (shorter half of leaf) 32--200(--210) \um, cell ends square, rounded or shortly fusiformly narrowed, differentiated alar cells 5--20. Sexual condition dioicous. Peristome: proximal outside of exostome varying from almost entirely cross-striolate to almost entirely dotted.


Common in many areas in the north, and in the Arctic, rich or intermediate habitats in fens, pools, lake shores or submerged in lakes; 0--3550 m; Greenland; Alta., B.C., Nfld., Man., N.B., Nfld., N.W.T., Nunavut, N.S., Ont., Que., Yukon; Alaska, Colo., Conn., Ind., Maine, Mich., Minn., Mont., Utah, Vt., Wis., Wyo.; South America; Eurasia; Australia.


Scorpidium scorpioides is usually easily known by its large size and strongly concave, broad and usually shortly pointed leaves with a short single or double costa. Straight-leaved phenotypes, which are rare, look very different from the falcate-leaved ones, but, except for the leaf curvature, there does not seem to be any difference between these phenotypes. Specimens with straight leaves could be confused with Pseudocalliergon turgescens and the differences between the two are given under the latter.