147 



the prcdoniiiiMiit lonn. here growini;' veiy dense and close. There ai'e also 

 dense striiis of considerable length on the shore along tlie northern end of 

 the lake. Its distrilmtion seems to be determined by the presence of solid 

 sand-beds or bars where it delights to grow. It generally grows wholly 

 on shore or in only (inite shallow Avater, and does not seem to like the 

 beating of waves so well as does N. Ji(<-ii.'<fri.<!. Fig. 3 shows a characteristic 

 set of relations (sontli of Chicago Hill invv). Willows on ice ridge at the 

 left. Sciriuis (iiiK ricdiiiis on sandy bank. N. laciistri-s in water with stems 

 on shore. A patch of I'oiifvdcrid (■(inliita in water in foreground. 



Fig. 3. 



PONTEDEJUA VORDATA occurs in small or isolated patches all around 

 the lake, but by far the largest and most continuous stretch is at the south 

 end, not a great way from the mouth of Clear Creek. This plant is gener- 

 ally associated with Xijiiiphaeo (idrciifi and is closely similar to it in 

 structure and habit. It generally forms a belt between the main mass of 

 Ni/mpJiaea and the shore. The Poiitedcria farthest from shore grows in 

 among the Xi/uiphdcd nearest the water's edge. Saf/ittariri, in so far as it 

 grows along the shore, occupies nearly the sani(> position, except that it 

 grows at the water's edge. Pnntedrria and \ uniiilidcd grow in considerable 

 abundance in the i)ond scutli of the lake, and Sdijittdrld !:as its brst de- 



