to each other in extent, and especially Acacia, which is made to 
include every Mimoseous plant which will not go into the other 
genera, are become numerous, unwieldly, ill-defined, and compara- 
tively unnatural assemblages of plants, which it is essential to, divide, 
in order to extricate them from the chaos in which they are involved. 
This has been partially accomplished by the separation of several 
new genera proposed by Brown, Arnott, Guillemin, and Martius; and 
the latter botanist has indicated what should be considered as the true 
genus Inga, but no one appears to have attempted to assign any 
definite characters to Acacia, which remains a confused mass of species 
which cannot be, or have not been, referred to any of the other known 
_Mimosex. Having myself had occasion very lately to describe those 
collected by M. Schomburgk, in British Guiana, I found it necessary 
to make an attempt at reducing the whole tribe of Mimosez to some 
kind of arrangement, and I there proposed three subtribes to. contain 
the twenty-eight genera now published; and, notwithstanding this 
_ great multiplication of genera, the average number of species in each 
will probably not fall far short of the total number contained in 
Linneus’s Mimosa, one of the most numerous in species known to him, 
and about five times his usual average. 
In defining the true genus Acacia another difficulty, however, 
presents itself—For which group should that name be retained? In 
following strictly the rules of nomenclature, the right might be 
claimed by that set of species which would include the gum Acacias 
of Africa; but on the other hand, these trees, most, if not all of them, 
are congeners to the Acacia Farnesiana which had already been sepa- — 
rated and well defined by Arnott, under the name of Vachellia, and 
since then by Gasparini, under that of Farnesia; and the more nume- 
rous set—that which includes all the Australian species, and many 
others both from the new and old continents, corresponds better with | 
Willdenow’s generic character, and has, as yet, received no other 
name. In retaining, therefore, the name of Acacia to this set in 
preference to the other, above two hundred fewer names are changed, 
and the rules of nomenclature cannot be said to be absolutely violated. - 
Amongst the numerous Australian species of Acacia, as thus limited 
and characterized at the head of this article, a considerable proportion 
have their leaves reduced to that state which are now usually called 
phyllodia. The first year from seed, indeed, more or less of the 
Jeaves are bipinnate, as in other Mimosee, but in the subsequent ones 
the folioles are never developed, but the petiole or main stalk is 
