28 MICHIGAN ACADEMY OP SCIENCE. 



4th. The latter fact is made (juite clear by the statement of Mr. Pieters 

 in regard to the Characetum. 



The microscopic plants of our lakes may be roughly divided into two 

 groups, those which attach themselves to plants and other objects in the 

 water and at the bottom, and those which freely move about. Many of the 

 larger Algae, such as Vaucheria, etc., and the fixed diatoms belong to the 

 first and desmids furnish examples of the second group. By microscopic 

 plant in this sense, those forms requiring the use of the compound micro- 

 scope for determining species are meant. Our knowledge of these plants 

 as found in Michigan waters is so limited that but little more can be said 

 in regard to them, but it is highly probable that they form both directly 

 and indirectly an important factor in the distribution and the supply of 

 fish in our lakes. With the facts above presented in regard to Lake St. 

 Clair in view, even though it is not a type of our smaller lakes, it will be 

 well to view the latter and see what bearing they may have in a general 

 way on the distribution of our lake plants. To anj- one who has visited any 

 number of the lakes which dot our Lower Peninsula, it will be easy to 

 recall the fact that in the deeper ones with abruptly sloping bottoms, the 

 amount of visible vegetation is small, being usually limited to a narrow 

 zone near the shore, and in the shallower ones, the amount is larger, the 

 plants extending farther out, and in very shallow ones covering the whole 

 surface. In most of these lakes, if not all, undoubtedly careful study would 

 reveal a certain correspondence in the essential features of the vertical 

 distribution of the macroscopic plants, mainly dependent on the width of 

 the various zones, which in turn would be found to depend on the slope of 

 the bottom. The species predominating in one lake would not necessarily 

 nor likely be the same, as it is frequently the case that one species will 

 secure the entire ground available to the type in a lake and monopolize the 

 field Avhile in an adjacent lake some other species or a group of specie w'ill 

 do the same. Mr. H. T. Blodgett writes me that in one small lake with which 

 he is acquainted the entire surface is covered with Utrioularia intermedia 

 so much so that during the blooming season the air is fragrant with its 

 sweetness, while in another pond connected with it, the much rarer itri- 

 eiiUiria imrpurea, is the exclusive plant. It is also true that certain species 

 colonize a jjortion of the shore of the lake and will not be found except in 

 that limited area. In the water which I have most carefully examined, 

 a mill pond made b}' damming Pine River, and consecjuently a shallow and 

 irregular basin, the predominating plants of the macroscopic flora, are 

 Elodea Canadensis in the shallowed portions and Eeteranthera graminea 

 in the deeper, but besides these there are at least nine species of Pota- 

 mogeton, all of which are fairly abundant, but more or less in colonies, 

 each species growing in limited areas by itself. Ranuneulus circlnatiis is 

 very common also in large patches, as is TaUisncria spiralis. In such a 

 pond the zones in larger bodies of water and natural lakes could not be 

 expected to be well defined, as the bottom is very irregular and the 

 deepest part is in the old river channel. Still, it is a noteworthy fact 

 that certain species are restricted to the deeper water and that the littoral 

 zone is fairly well marked and some characteristic species are abundant. 

 In this zone is the third recorded station of the rare hybrid Carer 

 JiipuUna.r retror.sa Dudley. 



Let us now consider briefly what ought to be done to redeem the reputa- 



