492 BOTANICAL GAZETTE [DECEMBER 
the species persists after such forms as Picea, Abies, and even Acer 
have established themselves. Among such forms only mature 
trees are to be found. These characters explain its distribution. 
In New England and the Laurentian region the time rate of change 
has been small. The forms which will eventually succeed this 
species have not had time to eliminate it. On the glacial moraine 
of the lake region this process of crowding out has in most places 
reached completion. 
UNIVERSITY OF BritIsH COLUMBIA 
VANCOUVER, B.C 
LITERATURE CITED 
1. BEAL, W. J., and WHEELER, C. F., Michigan flora. 1892. 
2. Bett, Rosert, Report on explorations of rivers draining into Hudson Bay. 
Geog. Survey Canada. 1879-1881. 
Bowman, IsataAu, Forest physiography. 1914. 
4. Briccs, L. J., and SHanrz, H. L., The wilting coefficient of different 
plants and its indirect determination. U.S. Bur. Pl. Ind. Bull. 2 and 3. 
Ig12. 
5. Bray, W. L., The development of the vegetation of New York State. 
New York State Coll. Forestry, Tech. Pub. 2. 1915. 
6. Cooper, W. S., The climax forest of Isle Royal, Lake Superior, and its 
development. ‘Bor. GAZ. 55:1-44, I§5-140, 189-235. 1913. 
Cow tes, H. C., The causes of vegetative cycles. Bor. Gaz. 51:161-183. 
w 
rs 
7 
IQII 
# 
, The physiographic ecology of Chicago and vicinity: a study of 
the origin, development, and classification of plant societies. Bot. GAz. 
31%:73-108, 145-182. rgor. 
9. DeForest, H., Recent ecological investigations. Proc. Soc. Amer. For- 
esters 60: I9gT4. : 
10. FERNOw, B. E., An analysis of Canada’s timber wealth. Forestry Quart. 
6: 337-353. 1908. 
ti. , Forest problems and forest resources of Canada. Proc. Soc. 
12. FROTHINGHAM, E. H., The northern hardwood - its composition, 
growth, and snaewenaelt U.S. Dept. Agric. Bull. 
13. FuLtER, Gro. D., Evaporation and soil moisture in ‘santo to the suc- 
cession of plant associations. Bor. Gaz. 58:193-234. 1914 
14. Harper, R. M., Car window notes on the vegetation of the upper peninsula 
of Michigan. Rep. Mich. Acad. Sci. 1914: 193-108. 
