BROWN — PLANT LIFE OF NORTH CAROLINA LAKES. 325 



in rice, but this is said not to have done well. Since that time the 

 canals have filled up considerably, and the lake has been for some 

 years about the same size as at present. From what has been said 

 it will be seen that the growth in the lake is of recent origin. 



In summer the temperature of the water rises from about 80° in 

 the morning to anywhere between 90° and 105° about midday. The 

 difference in temperature seems to be largely determined by the degree 

 to which the sun is obscured by clouds. 



The soil of the bottom was originally a coarse sand, but the inflow 

 from Great Lake and the interior current have carried humus and 

 small soil particles to certain places and have thus changed its char- 

 acter. The difference in the character of the soil seems to be the 

 chief factor in determining the local character of the flora, as the 

 different zones (to be described later) occur in the same depth of 

 water and have the same amount of light and heat. 



ZONES OF VEGETATION." 



The zones depending on the depth of the water, described by Magnin 

 (1893) for the lakes of the Jura and by Pieters (1894) for Lake 

 St. Clair, are not present in this lake, as the water is not as deep as 

 the deeper parts of the phragmitetum or outer part of the littoral 

 zone of Magnin. In Lake Ellis there are, however, three distinct 

 growths, all in the same depth of water, but occuring on different 

 kinds of soil. For convenience these will be called the central, 

 intermediate, and marginal zones. The plants of the marginal zone 

 are emergent forms, chiefly grasses and sedges, while most of the 

 plants of the other two are submerged. Figure 56 represents in a 

 diagrammatic way the distribution of these zones. 



The vegetation of the central zone is chiefly composed of Eriocaulon 

 compression either by itself or with Myriophyllum or with Eleocharis 

 robbinsii. 



The intermediate zone is characterized by PMlotria minor, 

 Sphagnum, Eleocharis inter •stincta, E. mutata, Panicum hemitomon, 

 Nymplmea advena, Castalia odorata, and Hydrocotyle. 



The plants of the marginal zone, as has been said, are largely 

 grasses and sedges. The chief species is Sacciolepis striata. 



To understand the disposition of these zones it is necessary to 

 examine the physical factors which have changed the character of 

 the surface soil in some places from a coarse sand to a fine mud. 

 The water coming through the swamp from Great Lake brings debris, 



« The suggestions of the Commission of Phytogeographical Nomenclature of the 

 Brussells Congress were not published at the time this paper was prepared. As no 

 misunderstanding can result from the author's use of the term "zone," it is not thought 

 advisable in his absence to disturb the form of the paper by substituting "girdle" as 

 proposed by the commission. — Editor. 



