58 
passes to one dominated by the tall grass Fluminia festucacea , with which 
occur Rorippa palustris var. hispida, Rumex maritimus var. fueginus, and 
Sium, suave . The Fluminia association is narrow and soon gives way to 
the broad Juncus-Calamagrostis association. Where there is standing water 
in the depressions there is a growth of Scirpus validus. 
A still less alkaline depression is indicated, at its margin, by an associ- 
ation of Typha latifolia , A triplex patula var. hastata, and Triglochin mari- 
timum, of which the first is the most abundant. The Typha may be at the 
edge of the pool or standing in the water. In very wet areas, Atriplex is 
replaced by a crowfoot Ranunculus (sceleratusf). Between the Typha zone 
and the Juncus-Calamagrostis association of the prairie there is a narrow 
zone of Eleocharis palustris , accompanied by Triglochin maritimum, Cala - 
magrostis canadensis, and Atriplex patula var. hastata. 
SINK-IIOLE MEADOWS 
A highly developed, and as yet uninvestigated, system of underground 
drainage in the upland areas of Wood Buffalo park has led to a type of 
sink-hole structure which is notable for its varying water levels. As 
stated elsewhere, completely drained holes have a vegetation that does 
not differ materially from that of the surrounding country, whereas very 
poorly drained holes develop muskegs at their margins. In a third kind 
of hole there is unmistakable evidence of the rise and fall of water levels 
amounting to as much as 50 or 100 feet. The slopes are nearly all of sand, 
and range from very steep grades of unstable materials to gentle ones 
covered with a turf. Many of the depressions are very irregular in shape, 
being made up by the coalescence of several holes in the vicinity. In such 
a one from which the writer made collections in August, 1929, there were 
terraces on the slopes and a small stream running through to the deepest 
hole. The formation indicates that the original series of large holes was 
later deepened by the falling of smaller holes within it and by the erosion 
of the former bottom. Figure 8 shows the arrangement of the topography 
at this place, which is along the Moose Lake-Pine Lake trail about 16 
miles from the former. Small streams, flowing from a lake just south of 
the hole, have supplied the water that has done the eroding of the deep 
gullies in the old bottoms. Beaver dams at the upper margins of the 
hole where the streams enter have undoubtedly modified the rate of flow 
and erosion to a certain extent. 
The steepest slopes, both of the newust depressions and of the older 
ones at higher levels, have a flora that depends upon the mobility of the 
sandy soil. Where it is loosely sliding it is being colonized by such plants 
as Equisetum arvense, Veronica peregrina var. xalapensis , and Artemisia 
canadensis. On more stable slopes are Hordeum jubatum , Potentilla nor- 
vegica var. hirsuta, St.achys scopulorum, Chenopodium album, Plantago 
major var. asiatica, Thalictrum venulosum, and Geum macrophyllum var. 
penneisum. On the newer slopes this association is a very open one, but 
it is much intensified on the old slopes of the original holes. 
The flora of the highest terrace, which appears to be the bottom of the 
older hole, has the most consistent type of vegetation for this kind of situ- 
ation. It is very common throughout the region and v r as studied to a 
