328 CONTRIBUTIONS FROM THE NATIONAL HERBARIUM. 



INTERMEDIATE ZONE. 



The intermediate zone borders on the inner side of the one just 

 described and has the same general shape. At the eastern end of the 

 lake this is 1,650 feet wide and is characterized by a dense growth of 

 PHlotria minor. Besides this, NympMea advena, Pontederia cordata, 

 Hydrocotyle, and Sagittaria are found in great numbers, and patches 

 of Panicum hemitomon and Eleocharis interstincta are scattered here 

 and there. Toward the sides of the lake this zone becomes narrower 

 and the soil is in general less muddy, resembling in this respect the 

 inner part of the zone at the eastern end. About halfway up the lake 

 the intermediate zone lias narrowed in places to a width of only a 

 few feet. Panicum Tiemitomon and Eleocharis interstincta are more 

 prominent, while the growth of PHlotria minor is much thinner. 

 Most of the other plants disappear to a great extent. In the second 

 fifth of the distance from the western to the eastern end of the lake 

 the intermediate zone becomes irregular. It runs along the marginal 

 zone and also appears as patches of Panicum hemitomon and Eleocharis 

 interstincta intermingled with the Eriocaulon compressum and Eleo- 

 cliaris robbinsii of the wings of the central zone. A few scattered 

 plants of Sagittaria are also found here. 



At the western end of the lake the intermediate zone is much nar- 

 rower than at the eastern end and the soil is in general less muddy. 

 Here Sphagnum takes the place of the PHlotria minor of the eastern 

 end as the predominant plant in the vegetation. This zone extends 

 around the tongue of grass of the marginal zone described above 

 as following the canal. Here Castalia odorata is found in great num- 

 bers, and it extends out into the canal for some distance after the 

 grass has disappeared. The other most prominent plant of this part 

 of the intermediate zone is Eleocharis interstincta. Where this has 

 fenced in small bodies of water, so that the debris from decaying plants 

 has not been washed away, patches of Castalia odorata are found. As 

 has been said, the soil is much less muddy at the western than at the 

 eastern end, and this probably accounts for the different character of 

 the vegetation found in the intermediate zone at the two ends. 



The vegetation is in general more vigorous toward the outer or 

 muddier edge of this zone than nearer the central zone. The water 

 lilies in the canal grow in very muddy soil and extend far out into the 

 lake. From these facts it seems probable that the soil toward the 

 outer part of this zone does not become unfavorable, but that the 

 plants of the intermediate zone are driven out by those of the 

 marginal. 



Since the soil of that part of the eastern end of the intermediate 

 zone which is nearest the marginal zone is muddier than the soil of 

 the intermediate zone at the sides and western end of the lake, it 



