DISTRIBUTION OF THE MORE PROMINENT NATURAL ORDERS. 239 



striking illustration of their prevalence. Out of a total of seventy-eight genera of the 

 Papilionaceee, only five are endemic, four of these being restricted to the Mexican region ; 

 thirty-two others do not extend beyond America, while forty-one, more than half, have 

 a wider range, and no fewer than thirty-four are widely dispersed. Passing to the 

 Caesalpinieae and the Mimoseae, it will be found that there is no endemic genus ; that 

 eleven of the genera are restricted to America, and that of the remaining twenty-one, 

 sixteen are widely spread. Such proportions are unapproached by any other exogenous 

 order of numerous genera, and only exceeded among the large endogenous orders by the 

 grasses, sedges, and rushes. The fact that eighty-four out of the 110 genera of Legu- 

 minosse occur in South Mexico and sixty-five of them in Panama gives some idea of the 

 richness of these floras, especially when it is considered that even these are still far from 

 having been fully investigated. 



Proceeding to the species of the Leguminosae some equally interesting facts 

 appear. 61 per cent, are endemic, chiefly in the Mexican region ; other 34 per cent, 

 are restricted to America, and 5 per cent, extend beyond America ; and of the forty- 

 seven species extending beyond America thirty-one are of wide range. Concerning 

 some of the latter it may be said that their present distribution may in part be due to 

 human agency, though all such as are probably of this category were eliminated before 

 the calculations were made. Twelve of the species of extra-American range are else- 

 where only found in western Africa ; and from what is known of the distribution of most 

 of the genera, the probabilities are that they are migrations from America ; but this 

 question is discussed in another place. 



A few additional facts respecting the distribution of genera deserve recapitulation 

 here. Thus, Lupinus, with the exception of a few annual species in the Mediterranean 

 region, is exclusively American, and numbers from eighty to one hundred species, 

 ranging from Canada and British Columbia to Uruguay and Chili, a vast majority of 

 the species being peculiar to the western side of the country ; no fewer than forty-four 

 coming within the limits of the " Botany of California." Only four or five species inhabit 

 the Atlantic States, and of these two are remarkable among North-American species in 

 having unifoliolate leaves. The genus is unknown in the West Indies and north- 

 eastern South America, but there are several simple-leaved species in Brazil. In 

 Mexico and Guatemala some of the species reach the altitudinal limits of phanerogamic 

 vegetation. Hosacfcia, Eysenhardtia, Petaloslemon, and Dalea are characteristic 

 American genera of temperate regions ; the last-named being essentially Mexican, and 

 numbering nearly a hundred species within our limits. It extends both north and 

 south, however, and two species are endemic in the Galapagos. The Cuban Dalea 

 tephrosioides, Griseb., is a genuine Indigofera, according to a manuscript note (extracted 

 from C. Wright's letters) in the Kew copy of Grisebach's 'Catalogus Plantarum 

 Cubensium.' Desmodium, a genus of very wide range, and numbering upwards of 

 150 species, is represented by about eighty in Mexico and Central America. There 



