10 Contributions from the Gray Herbarium 
Although the generic name (from dipep7s, two-parted, and 
oréupa, crown) was, probably through oversight, treated by 
Cassini as feminine (D. brasiliana), it is properly a neuter noul 
and is so used in this revision. : 
DIMEROSTEMMA Cass. — Heads medium or rather large, 
many-flowered, radiate or sometimes apparently discoid, the rays 
neutral; flowers all yellow. Involucre subtended by an outer 
1-2-seriate pseudo-involucre of leaf-like bracts, usually surpassiNg 
the disk; proper involucre 2—4-seriate, slightly graduated, about 
equalling disk, the phyllaries oblong, chartaceous-coriaceousor sub- 
coriaceous-scarious or the outer subherbaceous. Receptacle flattish 
or slightly convex; pales firm, keeled, enfolding the flowers. Rays 
small, oblong, neutral; disk-corollas with short tube and eylindnie 
throat, 5-toothed. Anthers sagittate at base, with ovate acutish 
appendages. Style somewhat swollen at base, inserted in a nectaly 
(2); style-branches oblong, bluntish, hispidulous, not appendaged- 
Achenes of ray sterile; of disk thickened, somewhat quadrangular, 
sometimes with more or less prominent intermediate ribs, narrow 
winged on the two main angles, glabrous or ciliate on the angles, 
their pappus of two strong awns continuous with the wings, the 
lateral angles sometimes prolonged into teeth or awns; the aw 
in one species connected at base by their lacerate decurrent 2. 
bases, but without the true corona of Oyedaea, — Erect simple - 
or sparsely branched perennials, probably suffrutescent at bas® 
bearing 1-12 heads; leaves opposite or alternate, ovate to orbiclr 
lar, veiny; the stem and at least the under side of the leave 7 
(except in one species) densely pubescent. 
Dimerostemma Cass. Bull. Soc. Philom. 1817. 11 (1817); 1. : 
1818. 58 (1818); Dict. Soc. Nat. xiii. 253 (1819); DC. Prod. vir 
255 (1838); B. & H. Gen. Pl. ii. 376 (1873); Baker in Mart. Fb 
Bras. vi. pt. 3, 231 (1884); Baillon, Hist. Pl. viii. 202 (1886), ™ 
small part; O. Hoffm. in Engl. & Prantl, Nat. Pf. iv. pt. 5, 230 — 
(1890). Serpaea Gardn. Lond. Journ. Bot. vii. 296 (1948), exh — 
S. oblonga. Oyedaea DC. subg. Serpaea (Gardn.) Baker in Mart 
L. c. 206 (1884). 
a. Plant green 

Nee 
pene ee 


, merely strigill . 4. D. retifolium- : 
a. Plant cinereous with a Be 
usually longer more or less spreading 
b. Heads solit. at apex of ste 
e Laws omerid [ ape: _ and branches, c 
icular, softly pilose-tomentose above. 2. D. vestitum™ — 
