520 BOTANICAL GAZETTE [JUNE 
morainal elevation on the east side of Park Lake, and is also char- 
acteristic of glacial sinks. Grasses do not form a close growth, but . 
other herbaceous species predominate. Troximon glaucum Nutt., 
Potentilla gracilis, and Valeriana edulis Nutt. are the principal 
associates. A society, the main representatives of which are 
DIAGRAM OF PLANT SUCCESSION, BOULDER PARK, COLORADO 
eadow (herbaceous or scrub) subclimax 
T rassland ji 
ee and Carex’ variabilis —__Willow thicket Carex Variabilis “rim” 
Selaginella + 
Fleocharis- Carex variabilis 
Ranunculus 
Mixed ass sociation Carex utriculata 
Eleocharis- Sparganium! 
Ranunculus Batrachiu. 
Glacial gravel of Flood plain: Flood plains — level Se a 
Pp 
high terrace (sand and sii (boulder) 
Erigeron macranthus Nutt., Campanula Parryi Gray, and Eriogonum 
subalpinum Greene, is characteristic of the meadow that imme- 
diately adjoins dry grassland. Associated species are Galium 
boreale L., Achillaea lanulosa Nutt., Stipa Nelsonii Scribn., Poa 
interior Rydb., and Koeleria cristata (L.) Pers. 
Discussion 
Based upon the water content of the initial ‘habitat, the suc- 
cessions may be classified as hydrarch and xerarch. The hydrarch 
