74 
It has been stated elsewhere that the balsam fir Abies balsamea finds 
its northern limit in the lower Athabaska valley. It was found in the 
Athabaska delta in the summer of 1930, near the head of Cree (Mamawi) 
creek, but has not been seen by the writer elsewhere in the district under 
discussion. In more southern regions it accompanies Canada spruce in the 
mature forests. 
Vegetation of Local River Deposits 
One of the commonest sights on the local river flood-plains and islands 
is the “ stepped ” or <£ banked ” vegetation that grows on them. It is accen- 
tuated during the summer months by the wide range in different shades of 
green which appear between the water’s edge and the spruce or poplar 
forest of the background. Although many random observations have been 
recorded throughout the flood-plain, detailed studies have been made at 
only a few representative places, namely, along Peace river just below 
Peace point, near the Government Hay Camp on Slave river, and on the 
large island that lies in Slave river at the 30th base line. The general 
topography of such areas has already been described. 
t 
HERBACEOUS ASSOCIATIONS 
The early stages of the river shore flood-plain vegetation seem to be 
determined by the soil and its configuration, which are in turn determined 
by the rate and activity of the current in the stream. Peace point is at a 
northward bend of Peace river, in the lower part of the district where the 
stream is confined by high gypsum cliffs on both sides. The blunt “ point ” 
itself is a low cliff of rock whose top is only a few feet above the spring 
high-water levels of the river. On the lower side of the point eddy currents 
have caused the deposit of a series of long, narrow flood-plains. These Have 
started with bars more or less parallel to the shore, which have been aban- 
doned as the general level of the stream has been lowered in recent geologic 
time. New bars are at present forming on the existing shore (Figure 5) 
which indicate the process. Flood waters of the present river cut back the 
outer sides of the bars, causing a sharply terraced appearance wuth the top 
surfaces of the terraces sloping backward away fi'bm the river. The fact 
that the same process has been going on at this place for a very long time 
is shown by the extension of similar topographic forms far above the 
present high water, and at considerable distance inland. Figure 5 is a map 
of Peace Point area showing the arrangement of these deposits. 
The shore is predominantly sandy, with prominent, well-drained bars. 
Consequently it supports practically no herbaceous vegetation on the lower 
levels, since such vegetation is of mud-flat or marsh type. Its first plants 
are sand-bar willows Salix interior var. pedicellata and the lowest bars 
have no plants whatever. The island bars at the 30th base line (Figure 
11, D) illustrate the same condition. 
The meander curves formed where the streams have less fall show the 
same general types of deposits except that the currents are much slower, 
causing bars and terraces that are very low and composed of finer, more 
muddy soils. These are well illustrated at the Government Hay Camp and 
at many places in the lower deltas (See Figure 11). Their initial vegeta- 
