DISTRIBUTION OF TRIBES. 441 
Melanthera is a small natural group of about eight species, di- 
stinct in the form of its achenes as well as in habit and minor 
characters, and common to tropical America and Africa. It has 
been divided into four purely artificial genera :—Melanthera proper, 
four American species without any female florets ; Lipotriche, one 
African species with fertile ray-florets ; JEchinocephalum, one 
American, and Wurmschnittia, one Abyssinian species with neutral 
ray -florets. 
Spilanthes is another natural genus, readily distinguished from 
its nearest allies by the truncate style-branches and other charac- 
ters, and widely distributed over the tropical world. It is diffi- 
cult without a detailed study to fix either the number of species, 
ranging between twenty and forty, or rightly to appreciate the 
geographical distribution of some of them. The greater number 
appear to be American; and one or two of these, as in Elephan- 
topus, range over the Old World; but a few also appear to be 
really of Old-World origin, especially two extending from the 
Indian archipelago into Australia. 
Coreopsis, in the extended sense in which we have taken it, neg- 
lecting, as in Melanthera, the differences between the neutral 
and the fertile ray-florets, contains nearly sixty species, and, 
although chiefly American, has established distinct forms in tro- 
pical Africa and in the Sandwich Islands. In America the range 
of the genus is wide, but chiefly northern, western, or Andine, 
and consequently not quite of so tropical a character as that of most 
American genera represented in tropical Africa. Several local 
American species or groups of species have been separated at 
various times as distinct genera characterized by the fertility or 
by the reduction of the pappus of the ray-florets, or by slight 
modifications in the margins of the achenes, dc. The African 
species were by some singular misconception of characters re- 
ferred originally to Verbesina ; they have since been established by 
Schultz Bipontinus as a distinct genus under the name of Presti- 
naria; but they correspond too closely to the Peruvian (shrubby) 
or Californian (herbaceous) Agariste to be generically separated 
from them. The Sandwich-Island Campylothece, united by A. 
Gray with Coreopsis and by Schultz Bipontinus with Bidens, must 
be regarded as an insular group almost as near to the one as to the 
other, although technically referrable to Coreopsis. The species are 
so varied, however, in habit and in some minor points of structure, 
that they could scarcely be kept together had not their geogra- 
