DISTRIBUTION OF TRIBES. 413 
ties; these are:—1. Psiadia, an African and Mascarene genus of 
about 14 species, with something of the involucres and yellow ray- 
florets of some of the Solidago group; but the ligule are as nume- 
rous and almost as small as in some of the Conyzoid genera. The 
glutinous inflorescence of several species recalls some of the 
South-American homochromous genera, whilst the shrubby habit 
brings it nearer to an African type; and the constant sterility of 
the hermaphrodite florets is also chiefly to be found in some 
South-African and Australian genera of the tribe. 2. Microglossa, 
a tropical African and Asiatic genus, as to which it still remains a 
doubtful point whether it should be associated with the Erigeron 
or the Conyza type. 3. Adelostigma, one, or perhaps two, tropical 
species of a truly African character, but seemingly connect- 
ing the Conyza type of Asteroidez, of which it has the tailless 
anthers, numerous filiform female florets, small achenes, &c., with 
the true Zaulee, which it approaches in habit and involucre. 
4. Parastrephia, a single Peruvian species which has been de- 
seribed as a Baccharis and as a Vernonia, and which Nuttall con- 
sidered to be anomalous in the whole order in having the female 
florets in the centre of the head surrounded by the hermaphrodite 
ones. But in this he was misled by insufficient specimens ; and 
the examination of more perfect ones shows it to be a connexion, 
as it were, between Conyza and Baccharis, technically belonging 
to the former group, but in habit, geographical station, and pro- 
bably in real relationship much more closely allied to Baccharis, 
where Meyen first placed it. 
7 (and lastly). The Baccharis type —This consists of two 
genera, including above 250 species, which may be loosely defined 
as more or less dicecious Conyzas. Although the florets in the 
capitula of Asteroides show so frequently sexual differences in the 
same capitulum, it is only in these two Baccharoid genera that 
there is any unisexuality in the capitula or the individual plants. 
In this respect they correspond with several Inuloide* (Plu- 
cheinez, Gnaphaliez, &e.), but have not the anther-appendages of 
that tribe ; and their geographical positionis different. Baccharis 
and Heterothalamus are exclusively American and chiefly South- 
American, where they accommodate themselves to every soil and 
climate, ranging over the tropical plains, dispersed over the moun- 
tain-regions in great abundance, and extending to the extreme 
south, although not accompanying other Andine and Magellanic 
genera over to the Antarctic or the Australasian region. They 
