DISTRIBUTION OF TRIBES. 397 
tralia, both monotypic, have each a much reduced pappus ; in Cen- 
tauropsis it is copious, but shorter than the achene, in Pleurocarpea 
reduced to the few exceedingly caducous sete of the American 
Centrathere, in Adenoon entirely deficient. In all three the 
involucral bracts are very persistent, quite different from those of 
the American Piptocarpha. 
2nd. Divergences in the receptacle.—In the Old World the 
receptacle rather deeply foveolate and fimbrilliferous, which has 
served to distinguish the above-mentioned Mascarene section 
Distephanus and the genus Bothriocline, a single tropical African 
species, is but little more than may be observed occasionally in 
several Vernoniacee of other genera, both in the Old and the New 
World, and even in Vernonia itself; in Distephanus it seems to be 
accompanied by some slight difference in habit, in Bothriocline by a 
peculiar involucre, as also by opposite or whorled leaves, a cireum- 
stance otherwise unknown in the whole tribe of Vernoniaces except 
in a single Brazilian, otherwise normal, Vernonia. In America, 
among the genera otherwise closely allied to Vernonia, the Bra- 
zilian monotypic Albertinia has the receptacle so deeply alveolate 
as completely to envelop the achenes; and the Mexican Bolanosa, 
also monotypic, has separate caducous pales embracing?each floret, 
with the habit, involucre, and other characters quite those of a 
Vernonia (Lepidaploa). Neither of the above characters, however, 
is of more than generic value, occurring in groups otherwise very 
far distant from each other. . The deeply alveolate receptacle is 
met with, for instance, in the Helianthoid Balduina from North 
America, and in several South-African Arctotidee. The deci- 
duous palez of Bolanosa occur here and there in species or genera 
of Eupatoriacee, Asteroides, Senecionidew, and other tribes 
usually deprived of them. 
3rd. Divergences in the pappus.—The indefinite sete of the 
inner or principal pappus of Vernonia assume a paleaceous 
character in several tropical American genera, otherwise nearly 
connected with Vernonia (Stilpnopappus and others); whilst in 
the Old World there is only a slight tendency in this direction, 
as already observed in some species of the section Stengelia, with- 
out being there carried further. On the other hand, the same 
paleaceous pappus prevails generally, though not universally, 
through the strictly American genera with glomerate capitula to 
be mentioned presently. This is, therefore, a type much developed 
in Ameriea, but early arrested in the Old World, or an old type 
