500 BOTANICAL GAZETTE [JUNE 
of different species. The principal invaders are Deschampsia 
caespitosa (L.) Beauv., Phleum alpinum L., Poa alpina L., Sporo- 
bolus brevifolius (Nutt.) Scribn., Carex variabilis Bailey, Salix 
chlorophylla Anders., S. padophylla Rydb., Sedum rhodanthum 
Gray, and Dodecatheon radicatum Greene. The occurrence here of 
a depauperate form of Erigeron eximius Greene is interesting, as 
Fic. 5. Mista of flood plain of sand and silt: note openness of vegetation, 
advancing clumps of Agrostis hiemalis and Alopecurus fuluus, and society of young 
Salix pee Rs and S. padophylla shrubs. 
is also the presence of such species as Festuca ingrata (Hack.) 
Rydb., Rumex acetosella L., Arenaria Fendleri Gray, Sedum steno- 
petalum Pursh, and Dasiophora fruticosa. In spite of the large 
number of species, the community is open. As vegetative develop- 
ment proceeds there is a reduction in the number of species and 
an increase in the number of individuals of the successful species, 
and increasing mesophytism of the habitat. 
