316 Annals of the Carnegie Museum. 



of the soil and the evaporation of the capillary water must be greatly 

 augmented by the great extremes of temperature through which the 

 soil often passes. ^^ Such a soil on Presque Isle becomes fitted for 

 plant-life much more slowly than does a soil of finer texture. 



(The Formation.) 



The ecological formation correlated with the sand-plain habitat 

 may, from its dominant species, be called the Artemisia-Panicum 

 formation. It is an open formation, the plants occupying approxi- 

 mately 20 per cent, of the entire area of the habitat. Towards the 

 lake the percentage of area covered is much less than farther back, 

 although in certain areas the plants may be considerably more aggre- 

 gated, especially in the older portion of the sand-plain near Long 

 Ridge, where the plants may even approximate closed conditions (see 

 Plate XXVIII). In the formation as a whole, however, there is prac- 

 tically no competition among the component species, the biological 

 element being of little importance in the ensemble of ecological 

 conditions. 



The facies of the formation is determined mainly by Artemisia — 

 A. canadensis diVid A. caudata — a.nd Fanicum 7>irgatiim, but there is 

 considerable alternation among these and a few other prominent 

 species, so that several consocies are to be recognized. There is also 

 considerable evidence of a succession among what are to be recognized 

 as consocies, as one goes from the youngest to the oldest parts of the 

 habitat. 



In the youngest part of the habitat, that nearest the drift-beach, the 

 formation consists essentially of the following consocies : 



(^) Panicum-Artemisia Consocies. 



(<^) Andropogoii fitrcatiis Consocies. 



(<:) Cladonia Consocies. 



*^ On the sand-plain at Cedar Point under almost exactly the same conditions as 

 may be found in various places on the sand-plain at Presque Isle, the author found 

 the temperature at a depth of one half inch below the surface of the sand, at 1:30 P. 

 M. on a clear hot August day to be 142° Fahr. The temperature recorded at the 

 Weather Bureau, at .Sandusky, just across the Bay, was 79° Fahr., maximum for the 

 day. The spot at which these measurements were taken was somewhat protected from 

 the slight breeze by a few surrounding oaks. 



.$■<?<? Jennings, O. E. "An Ecological Classification of the Vegetation of Cedar 

 Point." Ohio N^aturalist, 8: 291-340, April, 1908. 





