A Grammatical Dictionary of Botanical Latin

-chaetus,-a,-um (adj.A): in Gk. comp., of or pertaining to bristle, long hair; used for ‘stalk, foot, seta, i.e. a thin supporting bristle;’ having such or a specified bristle, hair; stalk, foot, seta [> Gk. chaitE (s.f.I), loose, flowing hair; of a horse’s or lion’s mane, the crest of a helmet (Liddell & Scott)]; see –chaetes,-is (three gender adjective).

Ending in –chaetus (masc.): achaetus [echaetus], anachaetus, ancistrochaetus, brachychaetus, heterochaetus, hypochaetus, isochaetus; microchaetus, pentachaetus, polychaetus, xanthochaetus.

BLEPHARIPAPPUS PENTACHAETUS [A. Gray], Bromus microchaetus; Cenchrus heterochaetus; Cereus polychaetus; Cereus xanthochaetus; Chiloscyphus polychaetus; Echinops macrochaetus; Haageocereus achaetus.

Heterosperma,-atis (s.n.III) achaetum. Ending in –chaeta (fem.): adenochaeta, chrysochaeta, macrochaeta, oligochaete, polychaeta, tetrachaeta.

Acronia tetrachaeta; Adnaria tetrachaeta; Adnaria adenochaeta; Aegilops macrochaeta, Allocarya oligochaeta

Ending in –chaetum (neut.): brachychaetum, dasychaetum, macrochaetum, microchaetum, phaenicochaetum, pterochaetum;

Achnatherum,-i (s.n.II) brachychaetum; Astrocaryum (s.n.II) dasychaetum; Allium macrochaetum; Astrocaryum dasychaetum. Heterosperma,-atis (s.n.III) achaetum.

Nouns in apposition ending in -chaeta, may resemble an adjective, but may be detected in binomials when the ending of the epithet does not match the gender of the generic name.

Nouns in apposition: in Amblystegium (s.n.II) megachaete, for example, the epithet is a feminine noun; Acaulon (s.n.II) leucochaete; Acaulon rufochaete Astragalus (s.m.II) dolichochaete; Atrichum (a.m.II) chlorochaete; Bactris (s.f.III) leptochaete; Bryum (s.n.II) brachychaete; Bryum (s.n.II) chrysochaete; Carterothamnus (s.m.II) anomalochaeta.

Centrolobium robustum var. macrochaete; the varietal epithet modifies the genus, not the species epithet, and is a noun in apposition.