86 College of Forestry 
DEVELOPMENT OF VEGETATION AS INFLU- 
ENCED BY THE SUBSTRATUM AND THE RE- 
SULTING INFLUENCE UPON THE  SUB- 
STRATUM! 
If the preceding account of the climatic relations of our 
vegetation resulted in giving a view of the movements and 
adjustments of vegetation in the large, it will seem dis- 
couragingly inadequate to account for the aspects of vege 
tation of any particular locality. No doubt in view of your 
common observations you will think of the zonal segregra- 
tion of our flora as a sort of theoretical construction. I can 
imagine the demonstrator pointing out the general domi- 
nance of sweet gum, oaks, hickories, tulip-tree and chestnut 
(af it had not been exterminated by chestnut blight) in 
the Bronx, and suddenly coming upon a hemlock grove, or 
a stony place with sweet fern and bayberry or a shallow 
pond of Peltandra. Also within excursion distance, cat- 
tail marsh, or a bog with Sphagnum, Chamaedaphne and 
southern white cedar (Chamaecyparis) or a hillside with 
mountain laurel. You get the conviction that vegetation is 
all jumbled together more or less haphazard. I am frank 
to say that, all along, as we tried to follow a consistent cli- 
matic segregation of species, we met, as in fact we do meet in 
the field at large, many instances where local conditions 
of soil or water table operate to nullify the effect of climatic 
factors. You can’t account for the status of our vegetation 
on either climatic or edaphie (the substratum in general) 
grounds alone. Nor will observations merely of the opera- 
tion of these factors suffice. On the basis of general knowl- 
edge and observation it may suffice to say that sweet gum 
and willow oak and persimmon and mistletoe do not 
1 The reader who may desire to go more fully into the literature of 
this subject of the development and structure of vegetation should con- 
sult the works of Clements, Cowles and their associate investigators and 
numerous others. See for example, Clements, F. E. The development 
and structure of vegetation. Rep. Bot. Surv. Nebraska, vii:1904; 
Cowles, H. C. The physiographic ecology of Chicago and vicinity. 
Pe ae 31:1901, and The Causes of Vegetative Cycles. Bot. Gaz., 
