144 



stemmed ii(iu;i tics -for length of stem seems to be the chief factor in de- 

 termining the liabitat. It shoukl l)e borne in mind, however, tliaf tlie 

 long-stemmed are quite variable in length, depending on depth in which 

 they grow, lii general tlH> inlinences which determine the habitat of 

 wholly submersed aquatics, aside from the kind of soil at the bottom, is 

 the amount of light (and probably dissolved gases) available. The amount 

 of light and dissolved gases is determined by the nearness to the surface. 

 The foi-mer is also determined by the clearness of the water; and in case 

 the clearness of the water is disturbed by organisms characterized by 

 holophytic nutrition, the amount of gaseous jilant food, as well as the 

 light, would be decreased with the increase of amount of suspended or- 

 ganic material. This feature of the case will be touched upon later. 



The short-stemmed aquatics i\iiius, Chara and the like) grow only in 

 shallow water. They were found out to a deptli of six feet of water, 

 i-arely more. 



Among the loiu/ aleiitined aqudtics I'otamogeton liia ii.s is gi-nerall.y found 

 in isolated patches, while MyriojihjiUinii. ('(■ivtopJii/llinii. and I'otamoncton 

 pectinatvs grew together, making long belts. These form the extreme cen- 

 tral belt of (phanerogamic) lake plants. They are to be found from loo or 

 150 to 600 feet from shore, accoi-ding to depth of water. By means of 

 dredging it was ascertained that these plants rarely or never grow out 

 much deeper than can be seen from a boat with favorable light. Twelve 

 feet was the greatest depth at which any were found. As they grew to 

 1)0 about six feet long, the distance from their tops to the s\n-face of the 

 lake varies from about six feet, at the deepest, to nothing at the shallow- 

 est places where they grew. During the latter part of August, 181M), when 

 the lake surface was quite low, due to a protracted drouth, some of the 

 plants of MuridjtliyUiiiii pro.jected up to the surface and tlie toi)s Hoaled, 

 but they did not seem to be thriving well. 



Toward the south-central part of the lake is a large bar, and its i»osi- 

 tion is marked on the water surface l>.v the presence of Potamogetons and 

 other deep-water plants. 



It is seen, therefore, that the greater part of the lake bottom is dcn-oid 

 of coarse vegetation, the plants making only a rather narrow l>elt nionnd 

 near the shore. The plants seem limited, moreover, to depths much shal- 

 lower than might be expected. Records of these species growing to con- 

 siderably greater depths are common. This limit in depth may i)erliaps 

 be partly explained by the large amount of dilfused matter to be found 



