Blake — Revision of Dimerostemma 9 
tham & Hooker next to Helianthus and said to differ from that 
genus, no true member of which is known from Brazil, chiefly in 
its discoid heads. Baker in 1884 in the Flora Braziliensis gave a 
Latin description based on Cassini’s original, but suggested no 
new disposition of the genus. Baillon in 1886 included under 
Dimerostemma (itself doubtfully retained) the genera Oyedaea, 
Serpaea, Zexmenia, and Lipochaeta. In the Pflanzenfamilien Hoff- 
mann placed the genus between Hleutheranthera and Perymenium, 
a position for which it is hard to find reason in Cassini’s published 
description, repeating Bentham & Hooker’s statement that the 
genus chiefly differed from Helianthus in its discoid heads. Com- 
parison of the published diagnosis of Dimerostemma with Gardner's 
Serpaea led me some time ago to believe that its true relationships 
were with this genus, and the recent acquisition for the Gray Her- 
barium, through the kindness of Dr. H. Lecomte and M. F. Gagne- 
pain of the Paris Museum of Natural History, of a photograph of 
the type in the Jussieu Herbarium, has shown that such is the case. 
This type is in very poor condition, consisting at the present time 
merely of a stem bearing one stem leaf, three branch leaves, and 
several peduncles without heads, but it is clearly a Serpaea and 
apparently identical with S. ovata Gardn. The name Dimerostemma 
Cassini, freed from its long obscurity, must accordingly be adopted 
for this genus. Cassini’s original description of the heads as dis- 
coid was undoubtedly due to the poor condition of his specimens, 
since S. ovata is a radiate species, and the one character by which 
for many years the genus has been distinguished proves, oddly 
enough, to have been a mistaken one. In one species, however, 
which must be referred to this genus, Viguiera ? retifolia Sch. Bip., 
the heads are apparently truly discoid, so far as may be jt 
from the single type specimen I have been able to examine, in the 
Kew Herbarium, but better specimens are required before this can 
be affirmed with certainty. : 
The present revision was prepared chieflyat the Kew Herbarium, 
where is to be found what is probably the best collection of this 
little-known genus. Through the kindness of Dr. Stapf fragments 
of all the species there have been acquired for the Gray Her- 
barium. The herbaria in which specimens are deposited are indi- 
cated by letters (B = British Museum of Natural History; G = 
Gray Herbarium; K = Kew Herbarium). 
