BFNA Title: Forrstroemia
Author: L. Stark
Date: April 29, 2008
Edit Level: R
Version: 2a

Bryophyte Flora of North America, Provisional Publication.htm


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XX. FORSSTROEMIA Lindberg, Oefv. K. Vet. Ak. Foerh. 19: 605. 1863 * [For Johan Erik Forsström, 1775--1824, Swedish pastor and collector]


Lloyd Stark


Secondary stems irregularly pinnately branched, produced in clusters of 1--5 on either side of annual vegetative growth intervals; paraphyllia absent; pseudoparaphyllia subfoliose to occasionally filamentous, entire; axillary hairs ca. 7, usually 4 cells in length, distal cells 3, hyaline and elongate, proximal cell short and pigmented. Stem leaves loosely appressed to imbricate when dry, erect-spreading to nearly squarrose when moist, widely ovate to ovate-lanceolate or ovate-linear, margins mostly recurved to leaf middle or above, entire or serrulate distally; apices acute to shortly acuminate; costae single or short and double, ending before leaf apices; cells thick-walled, smooth; median cells elliptic to linear; alar cells quadrate to transversely elongate, extending up laminal margins to ca. 1/3 leaf length. Branch leaves smaller, with similar features. Sexual condition monoicous (dioicous, and synoicous). Perichaetia having straight leaf tips, with 1-seriate paraphyses. Seta rather short, to 4.5 mm, smooth, reddish, straight when wet, twisted when dry. Capsule immersed to exserted, erect, cylindrical, stomata absent, annulus absent; operculum conical to erect or obliquely rostrate from conical base; peristome pale, hydrocastique, inserted below mouth of capsule, teeth 16, free to the base or rarely united proximally, linear-lanceolate, smooth, granulose or minutely papillose, occasionally perforate distally, divisural lines mostly straight or moderately zig-zag, lamellae and trabeculae low or absent, plates mostly symmetric, occasionally irregularly shaped, rarely with additional depositions externally, endostome segments rudimentary to absent, often fragmentary and adhering to exostome, cilia absent. Calyptra cucullate, hairy. Spores greenish, spherical, minutely papillose, mostly 20--30 \um.


Species 11 (2 in the flora): temperate North and South America, equatorial Africa extending south to the Cape; e Asia (India, Nepal); se Australia.


Forsstroemia species are epiphytic, or occasionally are found on rock. Sporophyte generations (cohorts) overlap in their development, with individual sporophytes requiring approximately 18 months to mature. As a result, embryonic sporophytes from the present year are found along the same stem with maturing sporophytes initiated in the previous year. Spores are dispersed in winter. This pattern of sporophyte maturation is shared with species in the related genera Alsia, Dendroalsia, Leptodon, and Neckera. The peristome teeth flex outward when hydrated, inward when desiccated (hydrocastique), allowing spore dispersal under wet conditions.


SELECTED REFERENCES Crum, H. A. and L. E. Anderson. 1981. Mosses of Eastern North America, Vol. 2. New York. Stark, L. R. 1987. A taxonomic monograph of Forsstroemia Lindb. (Bryopsida: Leptodontaceae). J. Hattori Bot. Lab. 63: 133--218.


1. Stem and branch leaf cells fusiform to linear, 4--8:1; costae weak, single or double . . . 1. Forsstroemia trichomitria


1. Stem and branch leaf cells isodiametric to shortly oblong, 1--3:1; costa single, extending beyond midleaf . . . 2. Forsstroemia producta


1. Forsstroemia trichomitria (Hedwig) Lindberg, Oefv. K. Vet. Ak. Foerh. 19: 605. 1863


Pterigynandrum trichomitrion Hedwig, Sp. Musc. Frond., 82. 1801; Leptodon trichomitrius (Hedwig) Sullivant & Lesquereux; L. trichomitrius var. floridanus (Lindberg) Grout; L. trichomitrius var. immersus (Sullivant & Lesquereux) Sullivant


Secondary stems usually subpinnately branched. Stem and branch leaves lanceolate, ovate-lanceolate, broadly ovate-lanceolate, oval, or deltoid, abruptly to gradually acuminate, often somewhat apiculate, 1--3 x 0.5--1.2 mm; costa single and weak or short and double, single costa extending 25--70% of leaf length; median laminal cells 25--80 x 5.5--11 \um. Sexual condition autoicous, often gonioautoicous. Seta 0.4--3.9 mm. Capsule immersed, emergent, or exserted, 1--2.3 x 0.4--1 mm; operculum 0.5--1.1 x 0.3--0.6 mm; exostome teeth smooth, minutely papillose or occasionally granulose, plates well-defined to warty and asymmetric. Spores finely papillose, mostly 18--30 \um.


Spores mature winter. Epiphytic, boles of hardwood trees, occasionally on rock and bark of evergreen trees, shaded, relatively humid areas, especially along streams; Ont.; Ala., Ark., Conn., Del., D.C., Fla., Ga., Ind., Ky., La., Md., Mass., Mich., Miss., Mo., N.J., N.Y., N.C., Ohio, Okla., Pa., S.C., Tenn., Tex., Vt., Va., W.Va., Wis.; Mexico; South America; e Asia, e Australia.


For Forsstroemia trichomitria, along the states bordering the Gulf of Mexico, immersed capsules (i.e., with short setae) are very common. However, from Virginia northward, capsules are nearly always either emergent or exserted. The two North American species of Forsstroemia rarely may form hybrids that have intermediate features of median leaf cell length, costal length, frequency of single costae, seta length, post-fertilization perichaetial leaf length, and peristome appearance (L. R. Stark 1987).


2. Forsstroemia producta (Hornschuch) Paris, Ind. Bryol. 498. 1896


Pterogonium productum Hornschuch, Linnaea 15: 138. 1841; Forsstroemia ohioensis (Sullivant) Lindberg; Leptodon ohioensis Sullivant


Secondary stems erect or somewhat curved. Stem and branch leaves imbricate, ovate to ovate-acuminate, 1.1--1.7 x 0.6--1 mm; costae single, extending 52--81% of leaf length; median laminal cells 13--23 x 9--12 \um. Sexual condition gonioautoicous, with perichaetia slightly more numerous than perigonia. Seta 1.3--2.1 mm. Capsule emergent or exserted, 1.2--2 x 0.4--0.7 mm; operculum 0.4--0.8 x 0.3--0.5 mm; exostome teeth with well-defined plates, smooth to granulose, occasionally with additional depositions on outer surface, entire to occasionally perforate or rarely cribose distally. Spores 15--35 \um.


Spores mature winter. Epiphytic on trees, also occasionally boulders; Ark., Mo., Ohio, Va.; ne Mexico; South America; Africa; e Asia; e Australia.


Forsstroemia producta is known from only five sites north of Mexico, with recent efforts to recollect in Ohio unsuccessful. The interval of fertilization is in late summer and autumn; growth intervals are usually defined by vegetative branches.