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Published In: Muscologia Recentiorum 4: 78. 1819[1818]. (Muscol. Recent.) Name publication detail
 

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general taxon notes:
Bescherelle (1892) reported the first Racomitrium species, R. subsecundum (Hook. & Grev.) Mitt. & Wils., from China. Subsequently, numerous species of Racomitrium were reported or described from the country, including Taiwan, by different authors (Brotherus 1929; T. Cao et al. 1998b; P.-C. Chen et al. 1963; C.-C. Chuang 1973; Dixon 1934; Frisvoll 1988; C. Gao 1977; T. Cao & C. Gao 1985; C. Gao & G.-C. Zhang 1983; Koponen et al. 1983; C. Müller 1898; Noguchi 1954; Paris 1908; Sakurai 1937; P. de la Varde 1918; M.-X. Zhang 1978). Among these studies, P.-C. Chen et al. (1963) listed 12 species of Racomitrium from China. C. Gao (1977) reported 11 species from northeastern China and T. Cao and C. Gao (1985) treated 15 species from Xizang. T. Cao (2000) and T. Cao et al. (1998b) enumerated 23 species of Racomitrium from Mainland China, Hong Kong, and Taiwan. Racomitrium aquaticum (P. de Beauv.) Brid. was reported from Shaanxi province by M.-X. Zhang; however, we cannot verify this record. The distribution of this species in China is questionable.
 
Racomitrium is characterized among other genera in the Grimmiaceae by the strongly nodulose lateral cell walls, especially at the leaf base, and by the cladocarpous plants with prostrate stems and often abbreviated branches. There are some 80 species of Racomitrium in the world, and about 60 of them are relatively well understood (Crosby et al. 2000). In this treatment, 22 species are recognized in China.

 

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5. Racomitrium Brid.   砂藓属   sha xian shu
Muscol. Recent. Suppl. 4: 78. 1819[1818]. Rhacomitrium Brid. ex Lor., Moosstudien 94, 163. 1864, inval. orthogr. var. Grimmia sect. Racomitrium (Brid.) C. Müll., Syn. Musc. Frond. 1: 806. 1849. Trichostomum sect. Racomitrium (Brid.) Duby, Bot. Gall. 2: 573. 1830.
 
Plants usually medium-sized to rather robust, yellowish green, dark green to brownish green, in dense, extensive mats or sometimes in loose tufts. Primary stems creeping or ascending, freely and irregularly laterally branched, sometimes with abundant short, tuft-like branches, more or less pinnately arranged; central strand not developed. Leaves closely appressed, erect, sometimes contorted or secund when dry, erect-spreading when moist, oblong-lanceolate to narrowly lanceolate, mostly keeled above, acute or acuminate and usually ending in hyaline, piliferous points, sometimes blunt or rounded at apex; margins often recurved, uni- or bistratose; costa single, strong, percurrent or excurrent; leaf cells mostly unistratose, upper cells irregularly quadrate or short-rectangular, sometimes linear, smooth or occasionally papillose, thick-walled, often with sinouse walls; lower cells elongate-rectangular to linear, very thick-walled, smooth or papillose, with lateral walls strongly nodulose; basal marginal cells often differentiated, consisting of one or a few rows of short, straight-walled hyaline cells. Dioicous. Perichaetia terminal or often terminal on lateral branches. Setae elongate, erect, usually twisted when dry; capsules erect, symmetric, exserted well above perichaetia, oblong-ovoid to oblong-cylindrical, usually smooth, sometimes wrinkled-striate on the surface; annuli well differentiated; opercula long-rostrate; stomata present at base of urns; peristome single with 16 teeth, linear or linear-lanceolate, more or less divided nearly to the base, densely papillose. Calyptrae conic-mitrate, often lobed at base, not hairy. Spores small, spherical, usually densely minutely papillose.
 
 
 

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1. Leaf apices ending in papillose, hyaline hair-points............................................................................................. 2
1. Leaf apices muticous or ending in dentate, not papillose, hyaline hair-points................................................... 4
2. Hair-points strongly coarsely dentate; leaf cells smooth; alar region not differentiated, in only one row of elongate-rectangular, hyaline cells.................................................................................. 17. R. lanuginosum
2. Hair-points less coarsely dentate; leaf cells papillose; alar region differentiated, in 3–5 rows of inflated cells..........3
3. Plants irregularly and remotely branched; costa disappearing well below the apex.................. 6. R. canescens
3. Plants pinnately branched; costa ending in the apex..................................................................... 10. R. ericoides
4. Leaves oblong-ligulate or oblong-ovate, rounded-obtuse at the apex............................................................. 5
4. Leaves ovate-lanceolate or lanceolate, acuminate or slenderly obtuse at the apex........................................ 6
5. Leaves oblong-ligulate, broadly rounded-obtuse, dentate at the apex; costa disappearing below the apex........
.......................................................................................................................................................... 1. R. aciculare
5. Leaves oblong-ovate, narrowly rounded-obtuse, crenulate at the apex; costa ending in the apex.......................
...................................................................................................................... R. aquaticum (reported from China)
6. Leaves muticous or with very short, dentate points; leaf cells with dense and small papillae...................... 7
6. Leaves ending in hair-points; leaf cells smooth or with large papillae......................................................... 12
7. Median and upper leaf cells rounded to subquadrate, very shortly rectangular; alar cells differentiated into an inflated, yellowish group................................................................................................................................. 8
7. Median and upper leaf cells rectangular to elongate-rectangular; alar cells not differentiated into a group, with one row of hyaline marginal cells............................................................................................................... 9
8. Leaf apices blunt; costa ending in leaf apex; plants densely pinnately branched................ 4. R. barbuloides
8. Leaf apices with very short, dentate points; costa disappearing below leaf apex; plants simple or remotely branched.................................................................................................................................. 14. R. japonicum
9. Leaves lanceolate, with acuminate and dentate apices; costa percurrent.......................................................... 10
9. Leaves ovate-lanceolate, with blunt apices; costa reaching 2/3–5/6 the laminal length................................. 11
10. Leaves slightly keeled, recurved throughout on both sides; basal cells linear......... 3. R. anomodontoides
10. Leaves strongly keeled, slightly recurved at lower part; basal cells elongate-rectangular......7. R. carinatum
11. Plants sparsely and irregularly branched; leaves broadly ovate-lanceolate, plicate............... 5. R. brevisetum
11. Plants densely and pinnately branched; leaves narrowly ovate-lanceolate, not plicate....... 11. R. fasciculare
12. Leaf cells distinctly papillose or bulging...................................................................................................... 13
12. Leaf cells smooth............................................................................................................................................ 15
13. Hyaline hair-points dentate; upper leaf cells unistratose at margins................................. 18. R. microcarpum
13. Hyaline hair-points smooth, not dentate; upper leaf cells bistratose at margins........................................... 14
14. Upper leaf cells rectangular to elongate-rectangular, bulging................................... 15. R. joseph-hookeri
14. Upper leaf cells subquadrate to short-rectangular, distinctly papillose.......................... 22. R. verrucosum
15. Upper leaf cells bi- to tristratose at margins.................................................................................................... 16
15. Upper leaf cells unistratose at margins............................................................................................................. 18
16. Leaves ovate-lanceolate, concave; alar cells differentiated into a small, yellowish group.................... 9. R. cucullatulum
16. Leaves lanceolate, keeled above; alar cells not differentiated, with one row of hyaline marginal cells.. 17
17. Upper leaf cells rectangular to elongate-rectangular, hyaline hair-points not dentate............ 8. R. crispulum
17. Upper leaf cells oblate to short-rectangular, hyaline hair-points dentate.............................. 21. R. sudeticum
18. Alar cells differentiated into a group of (2–)3–5 rows of yellowish cells................................................ 19
18. Alar cells not differentiated, with only a row of hyaline marginal cells..................................................... 20
19. Leaves straight, hyaline hair-points short, not dentate, sometimes absent; setae 0.5–0.7 cm long; peristome teeth linear-lanceolate............................................................................................... 19. R. nitidulum
19. Leaves often secund, hyaline hair-points often long, dentate, but length and dentation variable; setae 1.0–1.2 cm long; peristome teeth linear..................................................................................... 20. R. subsecundum
20. Hyaline hair-points dentate............................................................................................................................. 21
20. Hyaline hair-points not dentate....................................................................................................................... 22
21. Plants densely irregularly branched; leaf margins distinctly recurved on both sides.... 12. R. heterostichum
21. Plants sparsely irregularly branched; leaf margins somewhat recurved on one or both sides................. 16. R. laetum
22. Leaves lanceolate, hyaline hair-points very long (1–3 times longer than laminal length); upper leaf cells narrowly rectangular............................................................................................................ 2. R. albipiliferum
22. Leaves ovate-lanceolate, hyaline hair-points short, sometimes absent; upper leaf cells quadrate to short-rectangular......................................................................................................................... 13. R. himalayanum
 
 
 
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