BOTANY OF TERRA AUSTRALIS. 23 



This order is sufficiently distinguished from both the 

 others by the liypogynous insertion and valvuhir aestivation 

 of its corolla, which being perfectly regular differs in this 

 respect also from the greater part of LomentacccTc and from 

 all the Papihonacese. 



Nearly the whole of the Australian species of the Lin- 

 nean genus Mimosa belong to Acacia of AVilldenow, as it 

 is at present constituted ; and about nine tenths of the 

 Acacia3 to his first division of that genus, described 1)y him 

 as having simple leaves, but which is in reality aphyllous ; 

 the dilated foliaceous footstalk performing the functions of 

 the true compound leaf, which is produced only in the 

 seedling plant, or occasionally in the more advanced 

 state in particular circumstances, or where plants have been 

 injured. 



The great number of species of Acacia having this re- 

 markable economy in Terra Australis forms one of the 

 most striking peculiarities of its vegetation. Nearly 100 

 species have already been observed ; more than half of these 

 belong to the principal parallel, at both extremities of 

 which they appear to be equally abundant ; they are, how- 

 ever, very generally diffused over the whole country, exist- 

 ing both on the north coast of New Holland, and at the 

 south end of Van Diemen's Island. But though the leaf- 

 less Acaciee are thus numerous and general in Terra Aus- 

 trahs, they appear to be very rare in other parts of the 

 world ; none of the Australian species are found in other 

 countries, and at present I am acquainted with only seven ad- 

 ditional species, of which five are natives of th« intratropical 

 Islands of the southern hemisphere ; the sixth was observed 

 in Owhyhce, and is said to be the largest' tree in the Sand- 

 wich Islands ; the seventh is Mimosa sfellaia of Loureiro, 

 upon whose authority it entirely rests. 



The second order, Lomentace.e or CyESALPiNE.E, compre- 

 hends all the genera having perigynous stamina, a corolla 

 whose aestivation is not valvular, and which though l^^:: 

 generally irregular is never pa])ihonaceous. To these cha- 

 racters may be added the straight embryo, in wliich they 



