352 BOTANICAL GAZETTE [NOVEMBER 
occupying areas of an acre (half a hectare) or more, but there are 
several of considerable size. Portage and Whitmore" Lakes occupy 
one and one-fourth to one and one-half square miles (325-390 hee- 
tares), while Union, Straits, Four-Mile, Ore, Independence, ete., 
A STR IR TRS RE A- 
: 4 bate 
IG. 1.—Map of the Huron drainage basin. The boundaries of the paiete : 
moraine are shown by the lines —--—. The boundary between the clay ™ 
belt and the lake plain is marked by the line - - - - - : 
e 
cover a fourth to half a square mile (65-130 hectares). : ee the 
percentage of the tributaries lie in flat-bottomed dep ene 
surface approximates the ground-water level, consequently P 
: ur 
thousands of acres of swamp and marsh land. Everywhere oie 
small undrained depressions, some well above the average ae of 
water level, others containing lakes and bogs. It is also wo 
* Not connected with the Huron River by surface drainage. 
