406 
apparently from the lake at Tyersall. This water is quite clear, 
but where it runs to the lake, over some gravel and yellow clay, 
there is always a great quantity of this Alga. The streamlet after 
running along a channel cut for it in stiff clay enters a culvert and 
passes into the lake. The Alga is abundant on the dead leaves 
fallen into the channel and on the clay sides and bottom or the 
channel. In the lake where from silting the water is shallow with 
very little movement the Alga is extremely abundant covering the 
surface with a dirty orange unpleasant looking coat. In the deeper 
parts of the lake, there is none visible with the naked eye but it can 
be found on the Utncularia and other weeds which are abundant. 
It is also abundant where there are many fine roots of bamboos or 
other plants in shallow water, and seems very general in shallow 
water spots in ferruginous soil especially under shade. A . at ^ ing 
♦well at the foot of some bamboos contained a quantity of this Alga 
chiefly on the fine roots of the bamboos projecting into the well, 
and the natives who used it complained that the water produced an 
itching effect on the skin, and gave up using the well, which was 
then filled up and abandoned. Attempts were made to destroy this 
Alga in the lake where it was very bad by a solution ot copper 
sulphate. A strong solution was made and thrown upon the floating 
Alga by a squirt and also from a bucket. The Alga disappeared at 
once wherever the copper sulphate touched it having apparently 
sunk, but its place was filled again shortly afterwards and the spot 
was soon covered again with it. 
I collected a quantity of the water deeply coloured with this 
Alga from the inflow of the stream above the lake, and divided it 
into two lots in glass-stoppered jars containing about 3 pints fOO oz.) 
of liquid. The water was orange coloured and opaque or nearly so. 
To one jar I added ¥ V oz. of powdered copper sulphate. n a tew 
hours all the Alga had sunk to the bottom m a flocculent mass 
about an inch thick, the water above being quite clear. he Alga 
seemed to be dead but showed no definite signs o decomposition. 
The clear liquid above shewed no Algal or animal life, ihe un- 
treated jar remained as before, the liquid being opaque and dirty 
orange coloured. But in a few days most of the Alga sunk to the 
bottom in this jar also, though the water was not as clear and trans- 
parent as in the jar treated with copper sulphate. 
The orange colour of this plant is due to hydrated oxide of iron 
deposited in the gelatinous sheaths of the filaments and the zoogloea, 
and there can be little doubt that it plays an important part in the 
precipitation of iron oxide in clay and on gravel, etc. so as to form 
the rock commonly known here as laterite, if indee 1 is no 
origin of the whole of this rock. In clay it seems to grow on 
exposed surfaces and in cracks, through which a small quantity ot 
water runs or settles, and I have detected this organism in red lumps 
of clay in a cutting, in abundance in the stage of cocci dividing, 
fn clay cuttings in the Malay Peninsula I have seen roots growing 
through the soil, and exposed, being cut across by the formation of 
a road over which water was running slowly, and trickling down the 
bank. Where this occurred the roots were coated with one ot these 
