Cleistogenes is a genus of perennial grasses in the family Poaceae (order Poales), comprising about 13 species native to Eurasia. The genus was first described by Yi-Li Keng in 1934 (Sinensia 5: 147) and was for a time considered an invalid name synonymous with Kengia, but revisions to the Code of Nomenclature have restored Cleistogenes as the correct name.
Plants are tufted with many-noded culms and linear to linear-lanceolate leaf blades that often become inrolled when dry, with the lower blades typically disarticulating from the sheaths. The ligule consists of a line of hairs, sometimes on a very short membranous base. The inflorescence is composed of few-spiculate lax racemes spaced along a central axis or a sparsely branched panicle, with shortly pedicellate spikelets that are distant or loosely imbricate.
A defining feature of the genus is the regular formation of axillary cleistogamous spikelets concealed within the upper leaf sheaths — the trait from which the genus derives its name (Greek kleistos, "closed," and genes, "born"). These hidden spikelets ensure seed production even under unfavorable climatic conditions and generally have fewer florets, smaller hyaline glumes, and narrower lemmas with longer awns than the chasmogamous (open-pollinated) spikelets. The terminal spikelets are laterally compressed with 1 to several florets, membranous and very unequal glumes, and narrowly lanceolate to ovate lemmas that are 3–5(–7)-veined, keeled, and usually pubescent near the margins, with a bidenticulate or mucronate apex.
Species are concentrated in northeastern China (ten species, five endemic) and extend westward through Central Asia, Pakistan, and northwestern India to southern Europe and Turkey, and eastward to Japan. Most inhabit semi-arid regions where they serve as useful fodder.
Etymology
The genus name Cleistogenes derives from Greek kleistos ("closed") and genes ("born"), referring to the axillary cleistogamous spikelets that form concealed within the upper leaf sheaths. These closed, self-pollinating flowers are a defining feature of the genus and ensure seed production even under adverse conditions. The Chinese name 隐子草属 (yǐn zǐ cǎo shǔ) similarly means "hidden-seed grass genus."
Distribution
Cleistogenes is distributed across Eurasia, with the center of diversity in northeastern China (ten species, five endemic). The range extends from southern Europe (Spain) and Turkey eastward through Central Asia, Pakistan, and northwestern India to Japan, Korea, and the Russian Far East. Species also occur in Afghanistan, Kazakhstan, Kyrgyzstan, Mongolia, Turkmenistan, Uzbekistan, Siberia, the Caucasus, and the Primorye region.
Ecology
A large proportion of Cleistogenes species are plants of semi-arid regions, where they provide useful fodder for grazing animals. The genus is remarkable for its regular production of cleistogamous spikelets hidden within the upper leaf sheaths — these self-pollinating flowers ensure seed set even under unfavorable climatic conditions, giving the genus a reproductive advantage in drought-prone habitats.
Taxonomy Notes
The genus was first described by Yi-Li Keng in Sinensia 5: 147 (1934). The name Cleistogenes was for a time considered an invalidly published name and was treated as synonymous with Kengia (Packer, nom. illeg. superfl.), but revisions to the International Code of Nomenclature have reversed this, and Cleistogenes is now the accepted correct name. GBIF records 12 descendant species; Flora of China recognizes about 13 species worldwide, with ten in China (five endemic).
