506 BOTANICAL GAZETTE [JUNE 
that is, by the invasion of willow thicket. There is no vestige, 
however, of the first associations of these shores. Carex utriculata 
occupies the wettest part of the area. It is followed on all sides by 
the springy sedge moor of Hypnum, Carex variabilis, and C. 
canescens L. Here Carex variabilis is building upon the moss. 
The principal shrub succeeding C. variabilis is Salix chlorophylla. 
Oxbow lakes 8 and g differ in a marked degree from all others 
in the Park. It will be seen that they are the only lakes of oxbow 
origin that occur on the middle terrace. Obviously they are 
physiographically much older than those of the lower stream terrace. 
They are very shallow and annually dry up. In spite of their age, 
they have not filled to any extent. Rock and coarse gravel, with 
but comparatively little finer material between, make up the pond 
bottom. This lack of plant débris is associated with periodic 
drying, and the exposure of the area to the winds. Late in a 
particularly dry season, the level bottom becomes dry and the 
strong wirids blow away the material that accumulates. The 
chief associations over almost the entire lake bottom is an open one 
of Eleocharis palustris and Ranunculus reptans (fig. 6). Glycerta 
borealis and G. grandis are rare associates. About the shore edge 
Carex utriculata is slowly working inward.. Carex variabilis or 
meadow scrub may come to the water’s edge. A few clumps of 
Salix chlorophylla and S. padophylla at the edge are relicts of the 
old stream bank stage. Such individuals have numerous dead and 
dying branches. 
East Lake (figs. 8, 9) is an old oxbow of South Boulder Creek, 
from which it is now separated by about 250 ft. The intervening 
area is a sedge moor alternating with willow thicket. Through this 
the lake outlet feebly flows. The old shore line of the creek is 
distinct. Mertensia ciliata (Torr.) Don. and Senecio triangularis 
Hook., typical streamside plants in the region, may be found 
sparingly in the willow thicket of the lake. Salix chlorophylla and 
S. padophylla, with the two associated herbaceous species, are relicts 
of a streamside flora. There is further evidence of the oxbow origin 
of East Lake. The stream cut into the terminal moraine and made 
a strong curve toward the southwest, working into its bank almost 
at right angles. As is happening at many places in the present 
