252 APPENDIX. 



genera are endemic, and the rest are restricted to America, except the widely diffused 

 Eupatorium, one species of Aloma in Polynesia, and one species each of Ageratum, 

 Adenostemma, and Mikania, now having a wide range. It is remarkable that these 

 three genera are only represented in the Old World by one common American species 

 each; the inference is that they originally spread from America, especially as they 

 colonize freely. Eupatorium (149 species) and Stevia (68 species) contribute more than 

 four sixths of the species of this suborder, and there are thirty-seven species of 

 Brickellia, twenty of Ageratum, and fourteen of Mikania, leaving forty-one species 

 between the other seventeen genera. The Asteroideae comprise 208 species, referred 

 to twenty-three genera, only one of which is endemic ; but a large proportion only 

 extend into western North America. Baccharis, an exclusively American genus, is 

 the largest and most interesting. It is dioecious and comprises about 300 mostly 

 shrubby species, spread all over America, except the colder northern regions, though 

 much more abundant in South America than North. Forty-eight species are recorded 

 from Mexico and three from Central America. Some of the proposed Mexican 

 species are doubtless bad; on the other hand, more may be expected to occur in 

 Central America. Erigeron numbers twenty-eight species, and of the characteristic 

 North-American Aster there are nominally seven. The equally characteristic North- 

 American Solidago, of which Gray describes seventy-eight species, extends as far 

 as South Mexico, though the species are few. Next come the Helenioidese with 

 thirty-eight genera, ten of them endemic, and 173 species, whereof 116 are endemic. 

 Excepting one species of Flaveria in Australia, one species of Jaumea in tropical 

 Africa, and the South-African monotypic Cadiscus, the Helenioidese are American, 

 having their headquarters in Mexico. Twenty-four of the genera extend into 

 western, and half that number into eastern North America ; ten of them are mono- 

 typic, and there are twenty species of Pedis, eighteen of Porophyllum, seventeen 

 of Tagetes, and twelve of Hymenatherum. The Senecionidese, with only eight genera, 

 including three endemic, number 118 species, of which 106 are endemic. Senecia 

 contributes ninety-eight species, all except five endemic. Besides this widely-spread 

 genus only one other, Erechthites, extends beyond America, and it only to Australia 

 and New Zealand. All three of the endemic genera are monotypes. Here follow the 

 Vernoniacese with nine genera, including one endemic monotype, and sixty-four species, 

 of which forty-eight are endemic. Vernonia, a widely spread tropical and subtropical 

 genus of about 400 species, represents nearly five tenths of this suborder in our region. 

 In Brazil it ranks second both in genera and species. Next come the Mutisiaceee, 

 which are very thinly represented in all of Bentham's Old-World regions; but they are 

 at least six times as numerous in America, chiefly in South America, culminating in 

 Chili. Within our limits there are six genera, all of which extend to the Andes ; & and 

 forty-eight species, which, with the exception of seven extending a short distance into 

 western North America, are endemic. Of Perezia, the largest genus, there are twenty- 



