1904] WELD; BOTANICAL SURVEY OF HURON VALLEY 45 
5. Forest. Next comes the only tree that seems to be able to 
endure these conditions, the tamaracks, small ones advancing 
into the cassandra zone, in one instance even within 6% 
(1.8™) of the water and farther back larger trees 12-16™ 
(30-40°") in diameter (fig. 4). This forms a forest of one 
species of tree, constituting the grove west of the Jake. There 
the trees stand close together, and the shrub vegetation, cassan- 
dra in particular, is killed by lack of light. The forest floor is 
covered with dead brown needles, with only the occasional 
green of a moss, sedge, fern, or composite pushing through 
between the clumps of dead cassandra. This is one type of 
bottom vegetation in a pure tamarack woods. Where the growth 
of tamaracks is more open, particularly if the ground is rather 
wet, a great variety of leafy herbaceous undergrowth completely 
covers the ground. This is the case in a swamp near Cavenaugh 
Lake, where under the scattered tamaracks there is a rank 
growth of skunk cabbage, indian turnip, ferns, woodbine, grape, 
vervain, mints, elder, and juniper. In this case cassandra had 
not been present in the basin to dry the bottom. Another swamp 
near Whitmore, consisting of small trees close together, was 
found to be very wet, the roots of the trees creeping on top of 
the ground and densely covered with sphagnum, little else being 
present. No cassandra had been there. 
Into the pure tamarack forest at the first Sister Lake, where 
the conditions permit, namely in the grove on the northwest, the 
foliowing are now coming in: 
Prunus serotina, Acer dasycarpum, Populus tremuloides, Rhus glabra, 
Quercus rubra, Rubus villosus, Osmunda cinnamomea, O. regalis, Pteris 
aquliina 
Leaving the basin level and the forest and going up hill on 
the west side, we pass to ground that has been cultivated, now 
in meadow. A few feet up the hillside we come to a distinct 
zone of white vervain, about 1o (3™) wide, which winds 
around the foot of the hill, its position evidently determined by 
water supply. 
The succession of plant societies as s here described, which is 
ideally perfect on the north and northwest, has been modified 
