1C 



TXCT7EASE OF THE FOOD SUPPLY 



No. 72 



Fig. 4a. Potamogeton perfoliatus, Clasping-leaved Pond-weed. Collected by Mr. G. H. 

 Graham in a pond near Toronto, June 25, 1908. Reduced to about one-third natural 

 size. 



Fig. 46. Two leaves, one-half natural size, of a plant from Whitewater Lake, showing 

 the clasping base and the variation in size. Drawn by Mr. G. H. Graham. 



