犬问荆

Equisetum palustre L., Sp. Pl. 2: 1061. 1753; Baker, Handb. Fern Allies 3. 1887; Christ in Bull. Acad. Georgr. Bot. 11: 271. 1902, et ibidem 20: 46. 1910; C.Chr. in Meddel. Fran Gdteb. Bot. Tr. 44: 108. 1924; Iljin in Kom., Fl. URSS. 1: 108. 1934; Schaf f ner et L. C. Li in Bull. Fan Mem. Inst. Biol. Bot. 9: 131. 1939; Rothm. in Fedde, Repert. Sp. Nov. 54: 77. 1944; Herb. Pl. Northeast China 1: 15. 1958; Tagawa, Col. Ill. Jap. Pterid. 23. Pl. 6: 34. 1959; Valentine in Fl. Europ. 1: 7. 1964; Davis, Fl. Turk. ＆E. Eage. Isl. 33. 1965; Ic. Corm. Sin. 1: 117. 1972; Fl. Tsinling. 2: 26. 1974; C. N. Page in Fern Gaz. 11 (1): 33. f. 10. 1974: Y. L. Changet al., Sporae Pterid. Sin. 52, Pl. 5: 18-23. 1976; Fl. Henan 1: 11. 1981: Nakaike, N. Fl. Jap. Pterid. 5, f. 5. 1982: Fl. Xizang. 1: 32. 1983: Dixit, Census Ind. Pterid. 19. 1984: Kurata et Nakaike, Ill. Pterid. Jap. 4: 50. 1985: Fl. Intramong. 1: 65, Pl. 5: 5-8. 1985; H. S. Kung, Fl. Sichuan. 6: 85, Pl. 25: 6. 1988; Fl. Xinjiang 1: 13, Pl. 3: 3-4. 1992; K. Iwats., Ferns Fern Allies Jap. 43. 1992; Keys Vasc. Pl. WulingMts. 9. 1995; L. B. Zhang et H, S. Kung in X. C. Zhang et K. H. Shing, ChingMem. Vol. 84. 2000. ——E. palustre L. var. polystachion Weigel, Fl. Pem-Rug. 187. 1769; Herb. Pl. Nartheast China 1: 15. 1958. ——E. palustre L. f. polystachion Vill. Dauph. 1. 1876; Christ in Bull. Acad. Georgr. Bot. 11: 271. 1902. ——E. palustre L.var. szechuanense C. N. Page in Fern Gaz. 11 (1): 34, f. 3: b. f. 11. 1974.

中小型植物。根茎直立和横走，黑棕色，节和根光滑或具黄棕色长毛。地上枝当年枯萎。枝一型，高20-50 (60)厘米，中部直径1.5-2.0毫米，节间长2-4厘米，绿色，但下部1-2节节间黑棕色，无光泽，常在基部形丛生状。主枝有脊4-7条，脊的背部弧形，光滑或有小横纹；鞘筒狭长，下部灰绿色，上部淡棕色；鞘齿4-7枚，黑棕色，披针形，先端渐尖，边缘膜质，鞘背上部有一浅纵沟；宿存。侧枝较粗，长达20厘米，圆柱状至扁平状，有脊4-6条，光滑或有浅色小横纹；鞘齿4-6枚，披针形，薄革质，灰绿色，宿存。孢子囊穗椭圆形或圆柱状，长0.6-2.5厘米，直径4-6毫米，顶端钝，成熟时柄伸长，柄长0.8-1.2厘米。

产黑龙江、吉林、辽宁、内蒙古、河北、山西、陕西、宁夏、甘肃、青海、新疆、江西、河南、湖北、湖南、四川、重庆、贵州、云南、西藏。海拔200-4000米。日本、印度、尼泊尔、克什米尔、俄罗斯、欧洲、北美洲有分布。