﻿356 MR. G. BENTHAM ON THE MIMOSE.E. 



spreading southwards till stopped by the ocean, which it has been unable to cross even 



to Norfolk Island and New Zealand. 



The Ingece, or Mimosese with indefinite naonadelphous stamens, are exclusively 

 tropical, and show a very great American preponderance, although a few races also have 

 prospered in the Old World ; and the two hemispheres have very little in common. 

 There are no identical or closely representative species ; and even the genera or subgenera 

 are mostly distinct. America has 330 species in 11 genera or subgenera, of which two 

 only are slightly represented in the Old World, and the latter has 78 species, of which 

 only 9 are allied to American forms, the remaining 69 forming 4 genera or subgenera 



unrepresented in the New World. 



Of the American genera, I/ysiloma alone, with 10 species, is limited to the western 



tropics or West Indies; the other 10 genera or sub 



o 



g generally over 



tropical America, but specially abundant in the forest regions as well as in the Brazilian 

 campos east of the Andes. The Old-World Ingese are also mostly forest inhabitants. 

 Alhizziat with 40 species, is generally spread over the whole tropical region, with one 

 species exceptionally established in extratropical Australia. Clypearia, with 22 species, 

 and Serianthes, with 5, are limited to the Indo-Australian tropical region, the three 

 genera including many variable races of extended range. Archidendron is exclusively 

 Australian, with 2 species of limited areas. The 5 Asiatic or Mascarene Calliandrce 

 and the 4 Asiatic Mascarene or African SamanecBy are quite local and definite in cha- 

 racter, whilst their numerous American congeners are remarkable for their variabihty 

 and wide dispersion. 



Inga itself, including Affonsea^ 142 species, is remarkable for its simply, not doubly 

 pinnate leaves, a character otherwise unknown among Mimoseae, and in that suborder 

 developed in America only; for the Indian bifoliolate Callicmdra cynometroides must 

 probably be noted as a reduction of a doubly compound leaf to its simplest elements of 2 

 unifoliolate pinnae, not as a reduction of a simply pinnate leaf to a single pair, although 

 the double articulation of the very short petiole is not evident, as in the corresponding 

 American bifoliolate Galliandra hymenceoides. 



With regard to the local distribution of Mimosese in each of the several continents, 

 the subject Is too closely connected with the general flora of each, and therefore too 

 large to be treated of on the present occasion ; I would only add a few words on the 

 northern and southern extension of the suborder beyond the tropics. 



We have seen that in America the northern and southern extensions exemplified in 

 the genera I'rosopis, Mimosa, and Acacia have taken place in those groups only which 

 are, under the tropics, restricted to the western margin of the continent, a region where 

 the mountain-chain and the adjoining sea have allowed a certain continuity of physical 

 conditions still to exist, a continuity which may well have been much greater during 

 former periods. As a result, the new races produced north and south, although discon- 

 nected in character as well as in area, have in many instances remained closely repre- 

 sentative ; and this is in accordance with what has been pointed out in many other 

 classes of plants. In the Old World, however, as I have on other occasions observed, 

 the ranges of mountains and impassable deserts and seas run much more east and west, 



