144 



.stemmetl luinatics— for length of stem seems to be tlie chief factor in de- 

 termining the liabitat. It sliould l»e borne in mind, lioweviu". tliat the 

 long-stemmed are quite variable in length, dej^ending on depth in which 

 they groAA^ In general the influences which determine the habitat of 

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

 the amount of light land probably dissolved gases) available. The 'amount 

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

 The former is also determined by the clearness of the watea-; and in case 

 the eleai-ness of the water is disturbed by organisms charactei^ized by 

 holophytic nutrition, the amount of gaseous plant food, a>s:'we>li as the 

 light, would be decreased Avitk the increase of amount of ^stispeiiided ov- 

 ganic material. This feature of the case will be touched uiV6n' la teFi '>■>. 



The short-stemmed aquatics [Naias, Chara and the iike) !ga:oW only In 

 shallow water. They were found out to a depth of .six, feet so^ water, 

 rarely more. •:'-■ ■'Mo:\rr hudq otir 



Among the loufj stemmed aquatics Potamogeton luvem' is generally found 

 In isolated patches, while Myriophyllum, Ceratophylltim, and Potamotjetdn 

 Itectinatus gi-OAv together, making long belts. These form the. exti-eme- cen- 

 tral belt of (phanerogamic) lake plants. They are to be found f roia 100. :or 

 150 to 600 feet from shore, according 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 t6 

 l>e about six feet long, the distance from their tops to the surface of the 

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

 est places where they grew. During the latter part of August. 18ftJ>. when 

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

 plants of Myr'wiihyUum projected up to the surface and the tops floated^ 

 but they did not seem to be thriving well. 



Toward the south-central part of the lake is a large bar, and its posi- 

 tion is marked on the water surface by the pi-esence of Potamogetons and 

 other deep-water plants. 'mi "I; 



It is seen, therefore, that the greater part of the lake; bottoua,uis devoid 

 of coarse vegetation, the plants making only a rather narrow rbdt ar^Dund 

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

 lower than might be expected. Records of these species; igcowing. -to icioji*^ 

 siderably greater depths are common. This limit in depth maylperlwtps 

 be partly explained by the large amount of diffused ma^jtenitoiibe ifouml 



