561 



THE EUCALYPTS OF PARR A MATT A, WITH DESCRIP- 

 TION OF A NEW SPECIES. 



By Cuthbert Hall, M.D., Ch.M. 



(Plates Ix.-lxi.) 



In no genus of plants does the distribution of the species appear 

 to depend more on physical factors than is the case with the 

 Eucalypts. The natural barrier of the dry, hot, barren region of 

 Central Australia divides the genus into two main groups, the 

 Eastern and Western, very few species being common to both; 

 while the Main Dividing Range breaks up the Eastern group 

 into three subgroups, the coastal, the highland, and the inland. 

 Those that we are concerned with, belong to the coastal, though 

 several of them are also found on the highlands and inland. 



The Parraraatta District embraces an area 14 x 18 miles, and 

 in this no less than twenty-four Eucalypts occur, and possibly 

 there may be an odd tree or two of several other species, which 

 are to be found in places just outside this area. But these 

 twenty-four species are not regularly and evenly scattered around, 

 but follow definite lines of distribution, depending mainly on 

 soil-formation, but also other physical factors, such as prevailing 

 winds, elevation, humidity of atmosphere, di'ainage, proximity to 

 a stream, and distance from the sea-coast. Certain species are 

 found over the whole area, notably E. eugenioides and B. resini- 

 fera, while others are strictly localised. The seeds of these must 

 be constantly being carried on to adjacent localities, yet they do 

 not even seem to germinate, or, if seedlings spring up, they 

 perish at an early age, or are ci'owded out by other species. For 

 instance, I have never found E. longifolia growing in the north- 

 eastern quadrant of this area, yet it is very common on the deep 

 clay of the southern side. Again, it is very common to find 

 certain species, which are not at all closely related botanically, to 

 be constantly associated with one another. Thus E. hemiphloia, 

 E. crebra, and E. tereticornis very commonly occur together, as 



