In this work the varieties proposed in 1842 are cited 
as synonyms of Acacia arabica, as are Acacia Adansonu 
Guillemin & Perrottet and Mimosa adstringens Schu- 
macher & 'Thonning. 
The greater number of botanical works since the ap- 
pearance of Bentham’s first work have followed his inter- 
pretation of Acacia arabica as a widespread, polymorphic 
species with several well marked variants. Several author- 
ities, however, have considered the variety nz/otica to be 
a good species; a few have raised still others of Bentham’s 
varieties to specific rank. 
The immediate question that confronts us is the cor- 
rect name under the Rules for the aggregate species. 
Four specific epithets are involved, arabica, nilotica, 
scorpioides and vera. 
Acacia vera Willdenow' can be ruled out at once as 
an illegitimate name. It was superfluous when published 
since Mimosa nilotica Linnaeus, a valid name in all re- 
spects, was already in existence. 
Acacia arabica (uam.) Willdenow unfortunately 
must also be discarded. When Bentham united A. arab- 
ica (1788) and 4.vera (1806)[ A. nilotica (1758) ] as Acacia 
arabica, he failed to take up the oldest legitimate epithet, 
nilotica. Furthermore, Bentham reduced an older specific 
name (ni/otica 1753) to varietal rank under a species of a 
later date of publication (arabica 1783). This is not per- 
missable under the present Rules. The conditions must 
be reversed with Acacia nilotica adopted as the name for 
the species, while 4. arabica is reduced to varietal status. 
Thus for two reasons it becomes necessary to replace 
Acacia arabica by Acacia nilotica (1.) Delile. 
The situation is further complicated by the existence 
of Mimosa scorpioides Linnaeus. At the time when some 
' 4eacia vera Garsault Fig. Pl. Anim. Med. (1764) t. 95; Deser. 
Pl. Anim. (1767) 68 is an accidental binomial and has no standing. 
[ 96 | 
