A Grammatical Dictionary of Botanical Latin

thrix, gen.sg. trichis (s.f.III), abl. sg. triche, in Gk., the hair, both of man and beast: see (2) trich-, tricho-, -trichus,-a,-um (adj.A), -trichum,-i (s.n.II): in Gk. comp.; = L. capillus,-i (s.m.II), q.v.;

NOTE: the ‘h’ in the initial ‘th’ of the nom. sg. does not occur in the other [i.e. oblique] cases.

- [moss] Nomen graccae compositionis, apud Apulejum primum occurrens et Polytrichum commune designans, a [polys] multum et [thrix] capillus, propter calyptrae indumentum villosum, (C.Muell.), a name of Greek composition, first occurring [in the writings of] Apulius and naming it Polytrichum commune, from [Gk. polys] ‘many’ and [Gk. thrix] ‘hair, due to the villous hair-covering of the calyptra.

NOTE: coma,-ae (s.f.I), q.v., ‘hair, head of hair; tresses, locks’ is collective and decorative, as opp. to ‘thrix,’ which is the anatomical or physical form of hair.

Mimosa chrysothrix, gen. sg. Mimosae chrysothricis, “The name “chrysothrix” refers to the golden indument on the young fruits; Ramalina melanothrix, "with black sporogones. “

-thrix, -trichis (s.f. III): in Gk. comp.; -‘hair;’ this epithet is a noun in apposition. It functions as an adjective in an epithet but is declined like a noun irrespective of the gender of the generic name with which it is associated [> Gk. thrix, -trichos, s.f.III the hair, the beard]; see trich-, tricho-, -trichus,-a,-um (adj.A), -trichum,-i (s.n.II): in Gk. comp., hairy or hair-like, -haired, -trichous;

NOTE: not –trix,-icis (s.f.III), q.v., which is a female agent suffix.

         singular          plural 
Nom.    -thrix          -triches      ‘hair’ (s.f.III) 
Gen.    -trichis        -trichum 
Dat.    -trichi         -trichibus 
Acc.    -trichem        -triches 
Abl.    -triche         -trichibus

- brachythrix, with short hair; callithrix, beautiful hair; chrysothrix, golden hair; melanothrix, with black hairs; microthrix, with small hairs; oligothrix, with few hairs; pyrrhothrix, with fiery hair

Malacothrix; Thelypteris phacelothrix, phacelo-, 'bundle, fascicle'

Note: loss of the aitch (h) in cases other than nominative sg.