Description from Flora of China
Herbs, annual, biennial, or perennial [rarely shrublets or shrubs]. Leaves simple, usually palmately divided or cleft, sometimes entire or pinnately lobed, petiolate. Basal leaves usually forming a rosette. Cauline leaves opposite or alternate. Inflorescence terminal or axillary, cymose, bracteate. Flowers usually paired or occasionally solitary, actinomorphic, rarely somewhat zygomorphic. Sepals 5, imbricate, apex obtuse to caudate. Petals 5, distinct, sometimes clawed, apex rounded, retuse, or emarginate. Stamens 10, in 2 whorls, outer ones opposite to petals, inner ones alternating with petals, all with anthers or very rarely (in G. pusillum) 5 reduced to staminodes. Nectaries usually 5 and alternate with petals, rarely (in G. sinense) united into a ring. Ovary 5-locular, with 2 superposed ovules per locule; style distinctly 5-cleft. Fruit a schizocarp, long beaked, splitting into 5 1-seeded mericarps.
Primary leaf blade divisions are named segments and second ones lobes. The middle segment is measured from leaf blade apex to the insertion of the petiole with the leaf blade. The main sinus is measured from the leaf blade apex to the junction between the middle segment and the adjacent lateral segments. The second sinus is the deeper of the middle segment. Sepal length does not include mucro length. Fruit length is measured from the mericarp base to the apex of the stigmatic remains. The fruit rostrum length is measured from the mericarp apex to the base of the stigmatic remains including, when present, a narrowed apical part.
Five species recorded from China are of uncertain identity or are too poorly known to be treated here and are discussed unnumbered at the end of the generic treatment.
Geranium schrenkianum Trautvetter (Bull. Soc. Imp. Naturalistes Moscou 57: 53. 1882) is widespread in Kazakhstan and is expected to be found in Xinjiang. This species is a small annual, easily recognized by its palmately divided leaves, petals 3-4 mm with emarginate apex, and antrorsely appressed trichomes on stem, petioles, peduncle, and pedicels.
Species incertae sedis
Geranium camaense C. C. Huang in S. Y. Jin, Cat. Type Spec. Herb. China, 301. 1994.
Geranium platyrenifolium Z. M. Tan, Bull. Bot. Res., Harbin 6(2): 52. 1986.
Geranium tanii Aedo & Muñoz Garmendia; G. trifoliatum Z. M. Tan (1994), not Andrews (1805).
Geranium rubifolium Lindley, Edwards’s Bot. Reg. 26: t. 67. 1840.
Geranium solitarium Z. M. Tan, Acta Phytotax. Sin. 33: 608. 1995.
Geranium yaanense Z. M. Tan, Acta Phytotax. Sin. 33: 611. 1995.
About 380 species: cosmopolitan, especially in temperate and tropical mountains; 50 species (18 endemic, three introduced) in China.