408 BOTANICAL GAZETTE [DECEMBER 
It is also worthy of note that in the southeastern part of this 
region the bog flora is increased in variety by a large number of 
plants whose range is more southerly than that of the typical 
bog plants. Among these are Vaccinum corymbosum, V. 
atrococcum, Rhodora canadensis, Aronia arbutifolia, and Vibur- 
num cassinoides. Their distribution points to a northward migra- 
tion from the southern Appalachians.” 
VARIATIONS OF THE BOG FLORA IN GEOGRAPHIC RANGE. 
But the map has a still greater significance. The dark area 
represents the region in which most of these plants attain their 
highest physical development. Those who have seen the mag- 
nificent groves of tamarack in the north, attaining a height of 
thirty meters and a bole diameter of a meter, will appreciate 
this fact when they compare them with the stunted groups of 
the larch in the bogs near the southern and northern limits. 
Again, within this same belt, at least eight of the plants, the 
buckbean, cranberry, snowberry, rosemary, leather leaf, labrador 
tea, birch, and tamarack, are not confined to bog areas. They 
may be said to have there a wider life-range and are to be found in 
a variety of habitats. The tamarack, for example, is found on 
the hills and along most of the streams. With the black and 
and white spruce and pine, it makes up a large part of the forest. 
Here too the buckbean, leather leaf, Labrador tea, and birch 
occur along slow streams, and the rosemary, snowberry, and 
cranberry in moist ravines and rich woods. 
Just as striking, perhaps, is the fact that as we go in any 
direction away from this optimum region, the first plants to 
diminish in size and frequency of occurrence are the arborescent 
tamarack and birch. Then follow in close succession the shrubby 
forms, and finally the herbaceous species.% This is practically 
a reversal of the order of their coming into a new area, and, as 
we shall see later on, this may have some connection with the 
10 ADAMS, C.C., Southeastern United States as a center of geographical distri- 
bution of flora and fauna. Biol. Bull. 3:123. 1903. 
1 Scheuchzeria palustris is an exception, so far as its eastern distribution is con- 
cerned, and has about the same range as Betula pumila, but in the west it reaches 
its southern limit in Colorado and California. 
~~ 
