BROWN — PLANT LIFE OF NORTH CAROLINA LAKES. 329 



would seem that the plants of the marginal zone do not occupy the 

 soil at the eastern end as fast as the soil would support them. There 

 seem to be two reasons for this, the presence of competitors to be 

 driven out and the method of invasion by the plants of the marginal 

 zone. Single plants of the grasses and sedges of the marginal zone 

 are rarely found in the intermediate zone, but the plants of the 

 marginal zone seem to advance as a solid stand by means of their 

 rootstocks. 



CENTRAL ZONE. 



The central zone is found on the sandiest soil. This is in the cen- 

 tral part of the lake and occupies the greater part of it. Two wings 

 also extend far toward the shore in the second fifth of the distance 

 from the western to the eastern end. In this second fifth the soil is 

 very sandy, and in the center, where the water is about 22 inches 

 deep, there is almost nothing but a sparse growth of Eriocaulon 

 compressum. Toward the sides where the water becomes shallower, 

 15 inches or less, there is a growth of Eleocharis robbinsii. This 

 rarely extends into water over 15 inches deep and does not grow on 

 soil which would support the plants of either the intermediate or mar- 

 ginal zones. This growth is included in the central zone because of 

 its occurrence with Eriocaulon compression on sandy soil as well as on 

 account of the small size of the plant and its open growth. Eleo- 

 charis robbinsii extends in for 700 feet on the south side and 1,525 feet 

 on the north side. 



Proceeding in either direction from about the middle of the second 

 fifth of the distance from the western to the eastern end, the growth 

 of Eriocaulon compressum becomes more abundant and is soon 

 associated with a thick growth of Myriophyllum. This extends to 

 the intermediate zone. In that part of the canal which runs across 

 the lake and is not filled with grass or any of the plants of the 

 intermediate zone the Myriophyllum grows more luxuriantly than 

 elsewhere, showing that the increase in debris is not detrimental to 

 its success and indicating that when this gives way to the plants of 

 the intermediate zone it is because it can not compete with the more 

 vigorous vegetation found there. 



COMPARISON OF ZONES. 



The different zones are characterized by different plants, but at 

 the edges of the zones there is often the usual intermingling. 

 ' The mass of the vegetation characteristic of the different zones is 

 in proportion to the muddiness of the soil. Eleocharis robbinsii and 

 Eriocaulon compressum of the central zone are both small plants and 

 do not form dense patches, while Myriophyllum grows in a loose, 

 fluffy mass with little bulk. The plants of the intermediate zone are 



