320 MR. IT. II. W. PEARSON ON THE 
boulders of unaltered gneiss which crop out irregularly. The 
deposits vary in thickness from a few inches to 5 feet or more*. 
They are thickest on the tops of the hills and in the valleys, 
where, under suitable conditions, so much water is retained that 
a swamp is formed. On the slopes, in spite of the rainwash, 
humus accumulates, though in less quantity than in more favour- 
able situations; on the steeper hill-sides, channels sometimes as 
much as a foot in depth are cut into the humus by the water as 
it flows off the surface. "The soil is an almost pure humus, blaek 
or coloured dark brown by the admixture of mineral substances ; 
but apparently pebbles are always absent. It varies in con- 
sistency from a black mud to a powdery soil such as the wind 
will remove as dust, though this last condition is rarely seen, as 
it normally contains considerable quantities of water. The 
absence of earthworms is also remarkable, and is probably not 
without effect in contributing to the formation of a pure humus- 
soil (30). The reactions of the soil were mot observed; 
attempts have, however, been made to use it for gardening 
purposes at the Hakgala Botanie Gardens, and it has been 
found to be too “sour” to. be of any use. Mosses play no part 
in the formation of these deposits, except in the swampy hollows, 
where species of Polytrichum and Sphagnum are found t. Else- 
where they are principally formed from the remains of grasses 
and Cyperaceg, which both individually and specifically con- 
stitute the greater proportion of the flora. In the more swampy 
localities Eriocaulons are abundant.. The only tree found upon 
these *humus-patanas" is the Rhododendron, which is well 
kuown to flourish on sour humus (31). 
The humus disappears quite suddenly where the patana passes 
into forest. There is usually a tendency for such formations as 
this, especially when they have a swampy character, to eneroach 
upon the surrounding forest (32). This may be the case in 
certain localities where the humus-patanas are wet and swampy, 
but there is no evidence of such encroachment, and indeed the 
* A recent cutting made during the construction of a new road near Amba- 
wela (5900 feet) passes through a small swamp and exposes 10 feet of wet 
black humus composed of the parts of Eriocaulon Wightianum, together with 
Anaphalis oblonga, Exacum zeylanicum, Polygala glaucoides, Blumea flexuosa, Ke. 
t “True peat” is stated to be formed in the hollows on the Nilghiris, 
by “the growth and decomposition of a moss" Medlieott and Blanford. 
‘Manual of the Geology of India,’ Calcutta, 1879, p. 429, 
