Citation: DC., Prod. 6:158 (1838).

Derivation: Greek rhytidosis, from rhytis, a wrinkle; in reference to the wrinkled involucral bracts of the type species R. helichrysoides.

Synonymy: Pumilo Schldl., Linnaea 21:448 (1848).

Common name: None

Description:
Annual or perennial herbs; vestiture of non-glandular sometimes woolly-cobwebby hairs; leaves cauline, all alternate, or opposite towards the base, sessile, entire.

Capitula in terminal lax corymbs or clusters, homogamous, discoid; involucre broadly hemispherical to subglobular, several-seriate, remaining more or less intact in fruit; outer bracts scarious or hyaline, sessile; inner bracts longest, similar but with a herbaceous midrib, or with a broad glandular-pubescent claw with hyaline margins and scarious erect laminae; receptacle convex to conical, naked, pitted; florets numerous, all bisexual and fertile, 4- or 5-merous; corolla narrowly tubular in the lower half and broadly campanulate in the upper half (when 5-lobed and exceeding the involucre) or urn-shaped (when 4-lobed and much exceeded by the involucre); anthers tailed at the base; style branches linear, somewhat flattened, with a truncate to almost capitate papillose apex.

Achenes narrowly obovoid, attached obliquely and with an oblique summit, prominently papillose, all similar; pappus of several obovate to spathulate entire whitish scales.

Distribution:  An Australian genus of 7 species possibly representing a heterogeneous assemblage.

Biology: No text

Taxonomic notes: The 2 species (including the type, R. helichrysoides) assigned here to this genus differ in many ways but are remarkably similar in achene-type which is evidently not represented elsewhere in the Australian Compositae. R. multiflora is therefore, at least for the time being, retained here.

Key to Species:

1. Perennial herb 25-50 cm tall; vestiture of woolly cobwebby hairs; capitula on peduncles 1-4 cm long, in lax terminal corymbs, or solitary; florets exceeding the involucre	R. helichrysoides 1.
1. Annual herb 1.5-5 cm tall; vestiture of scattered long straight hairs; capitula sessile in clusters surrounded by floral leaves; florets exceeded by the involucre	R. multiflora 2.

Author: Prepared by L. Haegi