544 CONTRIBUTIONS FROM THE NATIONAL HERBARIUM, 
tham in the Genera Plantarum to Conyza (=.Eschenbachia), where 
it has since been allowed to remain, while B. hérte/la and B. mucro- 
nata, with the several similar species described in recent years, have 
been kept in Baccharis. This course is decidedly unsatisfactory, 
since it vitiates the characters of both Baccharis and Eschenbachiu, 
and it seems best to distinguish a new genus to receive these species. 
This genus, which I propose to call Hemibaccharis, in allusion to 
the fact that the staminate plant is indistinguishable from Baccharis, 
will then be distinguished from Baccharis by the presence of her- 
maphrodite flowers in the center of the pistillate heads, perhaps also 
by its compressed 2-nerved achenes; from. H’schenbachia by the pres- 
ence of staminate plants; and from Heterothalamus by the absence of 
pales on the pistillate receptacle and the presence in the pistillate 
heads of central hermaphrodite flowers. 
It may be noted that Cassini? ascribes subdioecious heads to the 
Jamaican Baccharis scoparia Swartz (type of the genus Sergilus 
Gaertn., retained provisionally by Cassini). He describes the inner 
flowers as male, with regular corolla, and the outer as similar in 
appearance, but actually female, with “corolla ambigué,” containing 
false stamens. Cassini’s observations were apparently based on ab- 
normal specimens, for those of this species which I have dissected 
are strictly dioecious. Staminate heads of Hemibaccharis sometimes 
show more or less abortive stamens in the outer florets, and the same 
condition is likely to occur in Baccharis, but the essential diagnostic 
feature of Hemibaccharis is the regular presence of hermaphrodite 
flowers in the center of the pistillate heads. 
In ZH. pringlet only the staminate plant is known: in //. salmeoides, 
H. androgyna, and H. corymbosa only the pistillate. The corollas 
of both sexes are pubescent with short erect subclavate hairs. In 
several species the anthers of the hermaphrodite flowers in the 
center of the pistillate heads are more or less abortive. 
The following key to the 15 species of the genus recognized is 
based chiefly on the material in the National Herbarium, supple- 
mented by a number of sheets from the New York Botanical Garden 
and the Gray Herbarium, for the loan of which I am indebted to 
Dr. N. L. Britton and Dr. B. L. Robinson. 
SYSTEMATIC TREATMENT. 
Hemibaccharis Blake, gen. nov. 
Polygamo-dioecious herbs or shrubs, often scandent, with alternate leaves 
and small, whitish, discoid or disciform (in one species radiate), cymose- 
panicled heads; involucre 8 to 5-seriate, graduate, of linear to lanceolate or 
ovate, narrowly scarious-margined, green-centered phyllaries; receptacle flat- 
* Dict. Sci. Nat. 37: 479, 1825. 
