Mr. Brown has, some years since, furnished us with many 
highly interesting remarks, in the appendix to the voyage 
of Captain Fiinpers ; where he has particularly noticed 
those Genera of the Australian Flora, Eucatyprus and 
Acacta, as being each, so numerous in species, and so exten- 
sively scattered over the whole country, as to form striking 
peculiarities of its vegetation—their respective aggregates 
moreover, if taken together, and considered with respect to 
the mass of vegetable matter they contain, (calculated from 
the size, as well as the number of individuals), exhibiting a 
proportion of the whole, perhaps almost equal to all the 
other plants of that continent. 
That two Genera, agreeing truly in a part of their eco- 
nomy, although of very different orders, should thus largely 
contribute towards that peculiar character of the Australian 
forest-vegetation, which has long since met the observation - 
of Botanists, is of itselfremarkable ; but there are two other 
striking facts connected with the forests of New Holland, 
that are highly interesting to physiologists, which all tra- 
vellers in those regions have remarked, but on which, few 
_ have reasoned. ‘These are the position of their leaves on 
the branch, and the gray or sombre aspect they give to the 
landscape. Neither, have escaped the scrutinizing obser- 
vation of Mr. Brown ; for, regarding the former, he has 
observed, that in those Genera, the leaves are vertical—in 
other words, instead of presenting their surface towards the 
stem, the margin is opposed. to it, so that both surfaces have 
the same relation to light : and in respect to the absence of 
vegetable lustre in the wilds of that continent, that philoso- 
phical botanist has, by microscopic investigation ascer- 
tained, that it is to be attributed to the equal existence of 
cutaneous glands (pores, or stomata of the epidermis of 
most authors) on both surfaces of the leaves. 
Why that vertical economy, which so uniformly takes 
place in the aphyllous Acacia, in the Eucaryrtt generally, 
and in species of certain Genera of Proteacem—a family also 
greatly dispersed, and presenting remarkable modifications 
in Australia—should thus prevail in that country, and that — 
both pagine should bealike furnished with cutaneous glands, 
it may be difficult to explain ; although it does indeed almost 
seem obvious, that, that deviation from the usual position of 
leaves generally, which takes place in those leading Genera 
in Australia, as well as the uniformity, and perhaps greater 
adaptation of both surfaces (by some peculiar absorbent or- 
ganization) to imbibe atmospheric moisture at night, have 
a reference to that known constitutional dryness of the 
country, 
