272 Mr. W. H. Pearsall. 



shore -would show the Wastwater or Derwentwater stages, a sheltered one the 

 Windermere or Ullswater condition, though the range of light intensities at 

 different depths would be similar in each case. 



Isoetes Mtella Jimcus fluitaus 



Littorella Potamogeton perfoliatus oooooooo 



E praelongiis iimii.iinM.ii P. pusillus 



~PiQ, 2. Depth distribution of characteristic species in the lakes named. The arrows 



show the light limit for vegetation. The thickened base line indicates the parts of 

 the lake shores normally silted. The frequencies for any species are based on the 

 total records for the lake, reduced to the relative proportions of Table IV. 



Apparent Exceptions: Hawes Water. — This lake is apparently^abnormal 

 (i) in its high proportion of Nitella, Isoetes being scarce, (ii) in the high per- 

 centage of its shore-line that is silted. It may be remarked that the second 

 abnormality explains the first, since silting tends to replace Isoetes by Nitella. 



