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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 of 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 Utricularia 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 bathing 

 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 of 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 f6o oz.) 

 of liquid. The water was orange coloured and opaque or nearly so. 

 To one jar I added oz. of powdered copper sulphate. In a few 

 hours all the Alga had sunk to the bottom ia a flocculent mass 

 about an inch thick, the water above being quite clear. The Alga 

 seemed to be dead but showed no definite signs of decomposition. 

 The clear liquid above shewed no Algal or animal life. The 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 indeed it is not the 

 origin of the whole of this rock. In clay it seems to grow on 

 exposed surfaces and in cracks, through which a small quantity of 

 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. 

 In 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 of these 



