president's address. 781 



i. Trimeiis Theory. 



" Trimen gives his opinion respecting the maintenance of a 



definite line of separation between the western boundary of the 



patanas and the forest. He says that ' In the course of vast 



ages a perfect equilibrium between the two floras [i.e., patana 



and forest] has been arrived at, so that now neither can encroach 



on the other : the patana plants are unable to exist in the dense 



shady forest, whilst the seeds of the forest-trees never get a 



chance even of germination in the closely occupied grass-land. 



So far as can be observed, this balance is now maintained without 



change.' " Pearson, however, shows that some change is taking 



place, though so gradually that it may be easil}^ overlooked 



(p. 307). 



ii. Ahhays Theory 



(as regards one patch of the patana) is that the outcropping of 

 "half-formed quartzite," v/hich disentegrates into "little else 

 than a quartz sand impi-egnated with iron, is entirely incapable 

 of supporting the usual forest vegetation with which the district, 

 except in this particular spot, abounds." 



Pearson shows that this explanation can only be a partial one, 

 and is dependent on geological data which are not forthcoming. 

 The same remarks apply to the plains of the Dorrigo, no adequate 

 geological data being at present available. The matter is of 

 direct economic interest, inasmuch as settlers require information 

 as to the soils. On the occasion of my trip, I made a carefully 

 collected series of soils from both plains and forest, but unfortu- 

 nately an accident happened to them while they were awaiting 

 analysis. Careful analyses of the soils, selected, if possible, by a 

 geologist, would, I doubt not, throw light upon the types of 

 vegetation that are at present borne hN the two kinds of land. 



iii. The, Grass-fire TJieory. 



The patana grasses are very coarse and wiry, and in their adult 

 condition are unpalatable to cattle. The graziers' custom is to 

 burn the grass annually to get a 5^oung growth of grass. "The 

 country is temporarily reduced to a blackened waste which 



