1. Sphaeropteris Bernhardi in Schrader, J. Bot. 1800(2): 122. 1801.
白桫椤属 bai suo luo shu
Tree ferns, large, usually with a single tall stem, with dense fibrous mass of roots at base of trunk. Fronds 1-5 m or more, most 2-pinnate-pinnatifid, not persistent and leaving distinct rounded scars on trunk, young uncurling fronds and stipe bases covered with scales; stipe stramineous or purple, smooth or with warts or spiny; scales on stipe pale or brown; cells uniform, similar in orientation, shape, size, thickness, and color, margin with teeth, setae, or cilia, apical cell dark or unpigmented. Sori orbicular, distant from margins, with or without indusia; spore surface fine, coarsely spiny, or perforate. x = 69.
About 120 species: S temperate and almost pantropical, but absent from Africa and Madagascar, maximum diversity in Malesia, north to Indochina, S China, Japan (Ryukyu Islands), and E Himalaya, south to New Zealand, Tasmania, and E Australia, ca. five species in the New World, including Central and South America and islands of the Caribbean; two species in China.
Plants of rain forests and tropical montane forests (variable in forest layer: in canopy, medium-canopy, or understory), ravines, forest margins, clearings, swampy areas, and disturbed areas, species of Sphaeropteris are all large plants and require space to grow, in general, in less-shaded conditions than those of Alsophila.
