FLORA OF TASMANIA. 
On the Tropical Australian Flora. 
There are no geographical or other features of the Australian continent which enable me to 
draw any natural boundary between temperate and tropical Australia. In selecting a botanical tropic 
of Capricorn, I hence have had recourse to the distribution of the plants themselves, and these must 
afford very vague data. The tropical Flora, in one form, advances further south on the west coast 
and on the central meridian than on the east, because of the absence of mountains, and hence of 
water, on the west, which causes combine to favour the prevalence of hot, desert types of vegetation, 
many of which advance even to Swan River. On the east coast again the climate is moister, and we 
hence not only find the most marked features of extratropical Australian vegetation,— Stackhouma, 
Boronia, Tetratheca, Comesperma, various genera of Epacridece, Leguminosa, Myrtaceat, etc., ad- 
vancing in full force as far north as Moreton Bay, lat. 27°, which I have somewhat arbitrarily 
assumed there to be the limit of the temperate Flora,— but Palms and other tropical forms run- 
ning down the coast almost to Bass's Straits. To the northward of Moreton Bay (judging especially 
from Mr. Bidwill's Wide Bay collections) not only do many temperate forms disappear, but tropical 
ones, — Malvaceae, Steradiacece, Acanthaceae, Euphorbiacea, Convolvulacea , Meliaceas, and Sajnn- 
dacece, Ficus, together with numerous tropical Indian weeds,— become a prevailing feature in the 
landscape. The Araucarias, according to M'Gillivray (Voy. Rattlesnake, 184G-50), begin at Port 
Bowen and advance to Cape Melville. Pandanus, according to the same authority, commences at 
Moreton Island. 
On the west coast I am puzzled where to draw the line. Judging from Drummond's her- 
barium, formed between the Moore and Murchison rivers (lat. 27° 30' S.), the vegetation is there still 
typically that of the Swan River, though much modified, and reduced greatly in number of genera 
and species. Sir G. Grey, in his adventurous journey from Port Regent to Swan River, enumerates 
various eminently tropical forms as occurring to the north of Sharks Bay (lat. 26° S.), as Nutmeg,* 
Araucaria* Calamus (abundant), Vines, many Figs, and Areca, together with a Banksia of Swan lliver, 
which he distinctly alludes to as being quite exceptional (p. 247). To the southward of Sharks Bay 
again, he met with Xanthorrhcea and Sow-thistle, f both of whose northern limits he gives as 28° S., 
and Zamia (lat. 29° S.). The parallel of Sharks Bay, I have hence assumed to be north of the posi- 
tion of the tropic of vegetation. 
In determining what may be called the tropic of vegetation, regard must be had not only to the 
latitude and isothermal lines, but to the abundance of the vegetation and its character : and, indeed, 
in such a country as Australia the latter elements are perhaps of the greatest importance, owing to 
the diminution northward of so many peculiar genera that make up a large proportion of the 
extra-tropical vegetation, and to the fact that the tropical Flora is so very poor in number of species, 
and deficient in such conspicuously tropical genera as Epiphytic Orchids, Palms, Ferns, Scitaminea, 
Taking all elements into consideration, of the vegetation, actual temperature, and relative hu- 
