BOTANY OF THE CEXLON PATANAS. 313 
finer loose surface-débris, except such as is retained by the roots 
of the grasses and other soil-binding plants, which on the drier 
patanas is very little. This is particularly noticeable at Banda- 
rawela, where the sides of the hills are bare of soil and support 
only a few deep-rooted plants on their stony surface: on the 
tops of the hills, where the surface is flat or slightly hollow, 
accumulation of soil does occur to some slight extent. The 
surface-drainage of the Uva patanas during the torrents of rain 
which fall at the beginning of the N.E. monsoon is a very 
remarkable sight: the streams which run off the slopes being 
loaded with fine débris * which makes no small contribution to 
the sandy character of the Mahaweli-ganga. 
This monsoon, which constitutes the rainy season of the 
eastern slopes of the plateau, coincides with the period of the 
vegetative activity of the Uva patanas. 
We have, then, in the Uva patanas a district, the greater part 
of which suffers a dry season of eight months’ duration, modified 
only by about one month’s rain which falls during the latter six 
of those months. During this period a constant and drying 
S.W. wind blows over the area and, the sky being usually 
unclouded, the surface of the ground is subjected to a severe 
baking by the rays of a tropical sun f. The rain which falls 
during the S.W. monsoon is distributed over a few days, and falls 
so rapidly that but little of it is absorbed by the ground; and 
this is even more strikingly the case with the very heavy 
rains of the N.E. monsoon, which remove such fine loose matter 
as is formed and render the accumulation of soil and humus 
impossible. 
On the more elevated patanas to the west, the conditions are 
* Vincent, Report on Conservation of Ceylon Forests; Colombo, 1883, 
p.72, $114. Vincent here makes a statement with which it is impossible to 
reconcile the above account of erosion on the Uva slopes, which is, however, the 
result of personal observation. Cf. also Tennent, ‘ Ceylon,’ p. 25. 
t In some rough determinations of soil-temperature obtained by placing 
the bulb of a thermometer at a depth of 4 inches in the soil, the following 
results were obtained :— 
Wilson's Bungalow ... 85° F. Oct. 18, 1897, at 12.15 r.m. 
Bandarawela ............ 790 F. » 80, , maximum, 
Haputale.................. 805 F. Nov. 2, , " 
Passara .................. 80? F. Aug.14, „ at 3.45 ru. 
Madulsima Ridge ...... 90° F. » 15, ,  atl11.90A.x. 
