Jan., 1916] Evaporation and Plant Zones 95 



here receives considerable exposure to the winds from the 

 prevaiHng quarter, obviously. The soil is almost pure sand, 

 averaging about four to six inches (1 to 1.5 decimetres) above 

 water level. The vegetation in this area so restricted is almost 

 exclusively Calamagrostis canadensis with scattered and small 

 individuals of Salix longifolia. 



The Phragmites Zone — Behind the Zone just mentioned the 

 sandbar extends for some distance, but is nowhere emersed. 

 The depth of water at this portion of the habitat fluctuates, 

 generally being less than three inches (.7 decimetres), and the 

 sand contains a considerable amount of organic material. 

 Phragmites phragmites flourishes here almost exclusively, the 

 only invaders being occasional sickly plants of Dianthera and 

 scattered small colonies of Spirodela polyrhiza. The luxuriant 

 tops of the Phragmites compel rather wide basal spacing of 

 the plants, giving room for such invasion as does occur. 



The Pontederia Zone — Along the inner or northeasterly 

 edge of the sandbar just mentioned the water again deepens, 

 composing an extremely sheltered zone, hence one very rich in 

 organic detritus. The water depth here ranges between six 

 and twelve inches (1.5 and 3 decimetres), and the dominant 

 species is Pontederia cordata while Sagittaria latifolia is present 

 in considerable amount, with Carex sp. and stragglers of 

 Dianthera and Sparganium. 



The Castalia Zone — The sandbar mentioned above is suffi- 

 ciently long to form a tiny sheltered cove to the northeast, as a 

 glance at the map will show. Actually this little cove is a mere 

 recess at the western end of the larger Ned's Cove. Needless 

 to say the bottom here is heavily covered with mucky organic 

 matter, and the water, which ranges from one to four feet 

 (.3 to 1.2 metres) is quiet. The conspicuous and abundant 

 species here is Castalia tuber osa, while there is a plentiful 

 admixture of Nymphaea advena, Nelumbo lutea, Utricularia 

 vulgaris, Potamogeton natans et sp. 



The Sparganium Zone — Fringing the northerly border of the 

 cove, but in other respects like the Pontederia zone which 

 fringes its western border, we find the next distinctly marked 

 type of vegetation, which is an almost pure stand of Sparganium 

 eurycarpum. 



The Typha Zone — Inside of the fringe of Sparganium just 

 mentioned, and extending in all directions until it encounters 

 regions seized by Phragmites, lies the clear-cut cattail habitat. 



