308 MR. H. H. W. PEARSON ON THE 
and planters shows that where the patanas in the vieinity of the 
western forest are protected from grass-fires, the forest slowly 
establishes itself upon the patana; and it isa well-known fact 
that, unless these fires are prevented, the patana encroaches 
upon the forest. We must then conclude that the balance 
between the two floras is not “now maintained without change” ` 
as Trimen believed, though such change as does take place is, 
for reasons which will be indicated later, so gradual that it may 
be easily overlooked. 
Gi.) Abbay's Theory. 
Abbay, in a letter to * Nature’ (13), gives the results of his 
examination of a small area of patana in the valley leading from 
Pussellawa to Rambodde, situated about 6 miles N. W. of Nuwara 
Eliya, and on the western side of the central range. He finds 
there an outcropping band of “ halt-formed quartzite” which 
disintegrates into “little else than a quartz-sand impregnated 
with iron, and entirely incapable of supporting the usual forest- 
vegetation with which the district, except in this particular spot, 
abounds.” And to this alone he attributes the development of 
patana-vegetation on the lower slopes of the valley. He further 
states that he was * informed that the same quartzite formation 
occurs in the Uva patana district ; " and he, therefore, believes it 
probable that all the other patanas, especially the larger ones, 
“owe their origin to the eropping out of this quartzite band." 
There is no further evidence to hand with regard to the structure 
of the Pussellawa and Rambodde valley, and presumably Abbay's 
account of it is correct; but whether he is justified in attributing 
the presence of a patana-flora on the lower slopes of the valley 
to its geological structure alone, is perhaps open to question. He 
is certainly incorrect in assuming that the same geological 
structure in Uva will also explain the existence of the patanas 
over a large part of that province. The occurrence of 
quartzite on the Uva patanas was denied by Heelis (14), who 
makes the comprehensive statement that “in the Uva patana 
district the rock is limestone,” a generalization which is, how- 
ever, far from being correct. There is in Uva a small local 
development of limestone only, but over by far the greater 
part of the patana-area the underlying rock is gneiss, whose 
decomposition - products do not materially differ from those 
