(6 

 (7 

 (5 

 (5 

 (4,5 

 (4,5 

 (8 

 (7 

 (6 

 (6 

 (5 



(2*, 3* 



(5 



(2,3 



(5* 



(6,7 



- (5 



(I 



(8 



(5 



(5 



(4 



(4 



(8 



(i, 2, 3, 4 



(i, 2, 3, 4 



(i, 2,3 



(4,5 



(5,6 



(6,7 



(7 

 (5 



Triosteum perfoUatum L., horse gentian. 



Eupatorium urticaefolium Reichard, white thoroughwort. 



Liatris cylindracea Michx., blazing-star. 



" scariosa Willd., blazing-star. 

 Aster sericeus Vent. 

 " linariifolius L., narrow-leaved aster. 

 " azureus Lindl., blue aster. 

 " cordifolius L., heart-leaved aster. 

 " macrophylliis L., heart-leaved aster. 

 Erigeron pulchellus Michx., Robin's plantain. 

 Solidago speciosa Nutt., goldenrod. 



" racemosa Gillmani Fernald, goldenrod. 

 " nemoralis Ait., goldenrod. 

 " rigida L., goldenrod. 

 " hispida MuhL, rough goldenrod. 

 " caesia L., goldenrod. 

 Antennaria plantaginifolia Richards, everlasting. 

 Xanthium canadense Mill., cockle-bur. 

 Rudbeckia hirta L., yellow daisy. 

 Helianthus divaricatus L., sunflower. 



" occidentalis Riddell, sunflower. 



Coreopsis palmata Nutt., stiff tickseed. 



" lanceolata L. , lance-leaved tickseed. 

 " tripteris L., tall coreopsis. 

 Artemisia caudata Michx., wormwood. 



" canadensis Michx., wormwood. 

 Cirsium Pitcheri T. & G., sand-thistle. 

 Krigia virginica Willd., dwarf dandelion. 



" amplexicaulis Nutt., dwarf dandelion. 

 Prenantkes alba L., rattlesnake root. 

 Polymnia uvedalia L., leaf cup. 

 Hieracium canadense Michx., Canada hawkweed. 



II. THE PRAIRIE ASSOCIATIONS 



Shallow lakes or marshes have apparently one of two destinies, 

 namely, either a forest or a prairie. East of Chicago the former succes- 

 sion is almost universal, but both are to be seen in this region. The 

 stages in plant succession are not always clearly in evidence upon the 

 prairie, but in the following list of species those of the low prairie (i), 

 usually comprising a Spartina and a Calamagrostis association, are 

 distinguished from those more characteristic of the Panicum and the Poa- 

 Andropogon associations of the higher prairie (2). Harvey has shown 

 (Trans. 111. Acad. Sci. 6: 1913) the average evaporation in a prairie asso- 

 ciation to be about equal to that of the oak dune and the water content of 

 the soil to be decidedly low during the summer months. Comparatively 

 undisturbed prairie areas are to be seen at Chicago Lawn and Ashburn, 111. 



12 



