a tremendous flow of water that forms a deep pool and is the 

 fount for a large stream. The pool is clear, the water hard, and 

 there is a luxuriant growth of Chara over much of the bottom. There 

 is also a scant development of Spirogyra spp. along the fringes of 

 the pool, while Oscillatoria spp. and Phormidium spp. encrust sub- 

 merged timbers and water-logged wood. The pool is bordered in 

 part by the vestige of a tamarack swamp, bedded with Sphagnum. 

 The water here is only slightly acid, and the algal flora in the 

 swamp is not rich in desmids as might be expected but very meager 

 and consists mostly of filamentous Zygnemataceae characteristic of 

 hard or semi-hard water situations. 



In the Lower Peninsula of Michigan, which is also underlain by 

 Paleozoic rock, there are five physiographic regions. The most 

 northern one, the Northern Upland, occupies roughly the upper 

 quarter of the Peninsula and is bordered on the south by a diagonal 

 line running northeast-southwest from Alpena toward Muskegon 

 on the west coast. The line swings north, however, before reaching 

 Muskegon and extends to the lake, passing up and around Man- 

 istee. The Northern Upland is characteristically a semi-hard and 

 soft water lake region; although some bodies are basic (pH 7.8, 

 for example) most of them are below pH 7.1 and some as low as 

 pH 4.2. Except for a few limestone exposures the region is deeply 

 covered with a sandy glacial drift which has formed innumerable 

 lakes and swamps. The result is that the algal flora is richer and 

 more varied than perhaps anywhere else in the state. There are 

 both acid swamps favoring a luxuriant desmid and Oedogonium 

 flora, and mineralized waters supporting a characteristic flora in 

 which planktonic blue-green algae predominate. Meager water 

 blooms develop in a few lakes of upper Michigan, which are alka- 

 line, which have an ample supply of carbon dioxide, and which 

 have been fertihzed by nitrogenous matter from tilled soil or from 

 human habitation. Such conditions are more common in the south- 

 ern part of the state, where water is harder and where the lakes 

 are frequently the eutrophic type. 



Southwest from the Northern Upland is the Michigan Lowland, 

 bordering Lake Michigan. To the southeast is first the Saginaw 

 Lowland, extending southwest from Saginaw Bay of Lake Huron, 

 then the Thumb Upland, including the Thumb' and the greater 

 part of central southern Michigan. In the Thumb Upland, hard 

 waters predominate and although there is an occasional kettlehole 

 type of tamarack swamp, most of the water is rich in calcium, and 

 the hard water ( cyanophyte-diatom ) flora prevails. Many lakes are 

 bedded with Chara, and numerous marl deposits are found in old 



[7] 



