Description from Flora of China
Polypodium parasiticum Linnaeus, Sp. Pl. 2: 1090. 1793; Aspidium parasiticum (Linnaeus) Swartz; Christella parasitica (Linnaeus) H. Léveillé; Cyclosorus aureoglandulosus Ching & K. H. Shing; C. damingshanensis Ching ex K. H. Shing; C. excelsior Ching & K. H. Shing; C. hainanensis Ching; C. orientalis Ching ex K. H. Shing; C. rupicola Ching & K. H. Shing; C. xunwuensis Ching ex K. H. Shing & J. F. Cheng; C. yandongensis Ching & K. H. Shing; Dryopteris parasitica (Linnaeus) Kuntze; Nephrodium parasiticum (Linnaeus) Desvaux; Thelypteris parasitica (Linnaeus) Tardieu.
Plants (30-)50-70(-100) cm tall. Rhizomes shortly to long creeping, including stipe bases with dark brown lanceolate scales. Fronds approximate to distant; stipes (10-)20-30(-40) cm, stramineous; laminae (20-)30-50(-60) × (8-)15-25(-35) cm, bases not narrowed (sometimes slightly narrowed), apices caudate-acuminate; lateral pinnae 10-15(-20) pairs, proximal 1 or 2 pairs reflexed; middle pinnae lanceolate, (5-)10-15(-20) × (0.5-)1-1.5 cm, bases truncate, lobed 1/2-2/3 toward costae, apices long acuminate; segments 20-25 pairs, 3-4 × ca. 3 mm (basal acroscopic one longer, sometimes crenate), obtuse to subacute at apices; veinlets 5-8 pairs, simple (ca. 10 pairs on basal acroscopic segment, occasionally forked), proximal pair anastomosing, sometimes next vein running to sinus membrane. Laminae herbaceous, brownish green or yellowish green when dried, with thin acicular hairs throughout on both surfaces, and reddish orange glands throughout abaxially. Sori orbicular, medial; indusia densely hairy. Sporangia bearing reddish orange glands on stalks. Spores with wings. 2n = 72, 108, 144.
The authors have not seen material of Cyclosorus parasiticus var. formosanus Ching (Bull. Fan Mem. Inst. Biol., Bot. 8: 205. 1938; Thelypteris parasitica var. formosana (Ching) C. F. Reed), described from Taiwan.
The type of Cyclosorus brevipes Ching ex K. H. Shing (FRPS 4(1): 336. 1999) is partly bipinnate-pinnatifid with veins and glands similar to those of C. parasiticus. It has no sori and only one gathering has been collected. This taxon might be a hybrid.
The type of Cyclosorus pauciserratus Ching & C. F. Zhang (Bull. Bot. Res., Harbin 3(3): 8. 1983) has no mature sori. Only one gathering has been made. This taxon might represent a young frond of C. parasiticus.
The types of Cyclosorus contractus Ching ex K. H. Shing (FRPS 4(1): 333. 1999) and C. parvilobus Ching ex K. H. Shing (FRPS 4(1): 338. 1999) both have the features intermediate between C. acuminatus and C. parasiticus. Each species has only one gathering (the type) with no sori collected. These two taxa might be hybrids.
Cyclosorus ×intermedius W. C. Shieh & J. L. Tsai (J. Sci. Engin. 24: 8. 1987) is endemic to Taiwan. It is the putative hybrid between C. dentatus and C. parasiticus.
Semi-open places in thickets, roadsides; near sea level to 1900 m. Chongqing, Fujian, Guangdong, Guangxi, Guizhou, Hainan, Hunan, Jiangxi, Sichuan, Taiwan, Yunnan, Zhejiang [N India, Indonesia, Japan, Korea, Laos, Myanmar, Nepal, Philippines, Sri Lanka, Thailand, Vietnam].