role of sedges in colorado plant communities 121 
Eleocharis 
Eleocharis acicularis, a small tufted spike-rush, is to be found somewhere 
along the shore of almost every lake or pond in the plains, foothill, and mon- 
tane regions of Colorado. It does not grow on a coarse-grained substratum, 
but becomes established in fine sand, in clay, or in loam. Being firmly 
fixed by rhizomes and fibrous roots and producing a dense matted growth, 
it is a good soil binder against wave action. In Boulder Park, at Tolland, 
Colorado, as shown by Robbins (9), Eleocharis acicularis is associated with 
Ranunculus reptans in forming the characteristic pioneer community of 
mud flats along streams. 
Eleocharis palustris, a much larger species, grows more in the water and 
often in almost pure stand, effectively filling up shallow pools in a few years. 
Both spike-rushes occur all the way from the plains to subalpine stations. 
A great many montane and subalpine lakes are, however, entirely free from 
Eleocharis lacustris. Its place is sometimes taken, ecologically, by Spar- 
ganium angustifolium. Other species of Eleocharis occur in the area stud- 
ied, but the writer has slight acquaintance with them. 
Cyperus 
Although five species of Cyperus are reported from Colorado, not any 
of them are conspicuous or important. They are confined to the plains 
region where they occur along streams and at margins of lakes or reservoirs, 
usually in wet, sandy soil. The commonest species is Cyperus inflexus, a 
rather diminutive annual confined to sandy shores recently exposed by low- 
ering of a lake level or shifting of a stream bed. Such habitats are likely 
to be occupied soon, if not in the first place, by Agrostis hiemalis, Eleocharis 
acicularis, or Alopecurus arislulatus. 
Eriophorum 
The species of Eriophorum, three in Colorado, are confined to habitats 
where the substratum is of a peaty nature. The writer has seen them only 
as very minor members in the Montane-Subalpine Sedge Moor Association. 
Dulichium, Fimbrystilis, Elyna 
These genera, represented in Colorado by one, two, and one species 
respectively, are of rare or unusual occurrence. The writer has made no 
observations of interest upon them. 
Carex 
Carex is well represented in northern Colorado. Unlike other genera of 
Cyperaceae which are practically all marsh plants, there are many species 
of Carex in mesophytic and xerophytic situations. In the following ac- 
