8 JAMES MURRAY 



colour, and is coarsely and irregularly wrinkled. It is composed of few or many 

 layers, like superposed sheets of paper. The lower surface of the sheet is of a dirty 

 green colour, and is composed of a tangled mass of many different algse, green and 

 blue-green. The whole mass was slimy to the touch. 



The mode of growth differs in different lakes. The broad sheets above described 

 are the commonest form. In Clear Lake it does not form flat sheets, but is coarsely 

 lobed and undulate, and can be seen through the clear ice growing up from the 

 bottom. In Coast Lake the lobed character is carried further, and little dendroid 

 masses of fine lobes can be seen embedded in the ice near the surface. When one of 

 these is cut out and thawed the plant loses its dendroid character and falls down to 

 form flat sheets. When the ablation of the ice of Coast Lake goes so far as to expose 

 part of the lake bed, it is seen to be covered with a deposit of small flakes of the 

 plant, in colour and appearance not unlike used tea-leaves. 



In a lake near Cape Barne the ablation of the ice exposed small masses of the 

 weed in which the successive superposed layers made up a thickness of six inches. 

 The layers were very thin and the colour a fine pink. 



Large fragments dredged from the bottom of Clear Lake and dried on blotting- 

 paper had a glossy surface and ash-grey colour like some of the lichens of the genus 

 Peltigera. In most other samples the surface was dull when dried. 



Under the microscope the brown weed is seen to be composed of a felt of very 

 fine fibres, crossing one another irregularly in all directions. Usually no definite 

 structure can be detected in the fibres, but Mr. Scourfield noticed some in which an 

 obscure division into cells could be seen. 



In some ponds we found another weed of very similar colour and appearance, but 

 in very small quantity. This was definitely composed of moniliform rows of cells of 

 some blue-green alga, very probably of the large olive-green laminae which we got in 

 some streams and ponds in summer. The similarity of the two suggests that the 

 commoner brown weed has in like manner originated in the blue-green filamentous 

 algaa generally associated with it. Plausible though the suggestion is, it requires 

 expert investigation before we can decide upon it. The filaments (Oscillatoria ?) 

 seem inadequate to the production of such masses, being to a large extent in the 

 form of longer or shorter rods (as shown in Plate IV. Fig. 15). 



The method of trenching a lake in order to get at the sheet of vegetation at the 

 bottom is illustrated in the accompanying diagram (Fig. 2). 



The shallow lakes were very easily trenched, a few hours' work sufficing to reach 

 the bottom. The trenching of the deeper lakes, Clear Lake and Blue Lake, was a 

 more laborious undertaking. The trench is marked out by a draft cut with the ice- 

 pick, enclosing an area of about six feet long by three feet wide. The whole surface 

 is then picked over to a depth of a few inches, and the chips are shovelled out. A 

 very little chipping seems to make a great depth of chips, and frequent clearing out 

 is necessary, or it becomes impossible to get at the solid ice on account of the loose 



