780 president's address. 



W. Pearson has an important paper on " The Botany of the 

 Ceylon Patanas" (Journ. Linn. Soc. xxxiv. 300), and much of the 

 information contained in his paper (which inckides an excellent 

 bibliograph}'') will be found full of suggestion to us. Patanas 

 " are grassy slopes and plains of considerable extent occurring at 

 all elevations above 2,000 ft." " Remarkable savannah-like 

 expanses in an otherwise forest-covered country" (pp. 300, 301). 

 They correspond, in fact, to the plains of the Dorrigo and other 

 portions of the northern tableland. 



Where the patanas come into contact with the western forest, 

 the boundary lines'^ are remarkably sharp and abrupt, though 

 quite irregular and in no way related to any physical features of 

 the land (p. 305). This also corresponds to the condition of 

 things in the New South Wales localities cited. " In the east, 

 the patanas pass gradually into an open park-like forest consisting 

 of low xerophytic trees and an undergrowth of grass " (p. 306). 

 To what extent the Dorrigo plains differentiate into an oj)en 

 park-like forest is a matter for further enquiry, and careful 

 examination will show how much of the vegetation may be properl}'" 

 termed xerophytic. " The existence of extensive, comparatively 

 barren, patana-areas in the midst of the luxuriant sub- tropical 

 growth of the montane region, and, more particularl}^, the manner 

 in which they abut upon the boundary of the western forests, 

 have attracted the attention of many observers." To account for 

 the existence in such close proximity of two floras so widely 

 different, three theories have been advanced (p. 307) : — 

 i. Trimen's Theory, 

 ii. Abbay's Theory, 

 iii. Grass-fire Theory. 



* The line along which two plant societies meet has been called the tension 

 line, whether between forest and heath or forest and prairie (plain, in the 

 Dorrigo sense). Here it is that the struggle is most pronounced. If the 

 other ecological factors remain constant, the tension hne does not change. In 

 that case, for instance, the forest does not advance on the heath nor the 

 heath on the forest. But, as will be shown in the discussion of the historical 

 factors, the conditions, as a rule, are changing constantly. Not only may 

 the struggle be between the forest on the one hand and some other type of 

 plant society on the other, but it may be between different kinds of forests. 

 (H. N. Whitford, op. cit. p. 293). 



