Hollyfern

Description

Polystichum is a genus of about 260 species of ferns with a cosmopolitan distribution. The highest diversity is in eastern Asia, with about 120 species in China alone; the region from Mexico to Brazil has nearly 100 additional species; Africa (17 species), North America (15 species), and Europe (5 species) have much lower diversity. Polystichum species are terrestrial or rock-dwelling ferns of warm-temperate and montane-tropical regions (a few species grow in alpine regions). Many ferns of this genus have stout, slowly creeping rootstocks that form a crown, with a vase-like ring of-evergreen-fronds-30 to 200 centimetres (10 to 80-in) long. The-sori-are round, with a circular indusium. The stipes have prominent scales. The genus differs from the well-known and allied fern genus-Dryopteris-in the indusium being circular, not reniform, and in having the leaf blades with asymmetrical segments-one side of the segment is much longer than the other at the base. Several species are grown as ornamental plants in gardens, notably P. setiferum. One species, P. tsus-simense of eastern Asia, is commonly offered as a houseplant.