No. 385.] FORESTRY AND GEOLOGY. II 
because their limits of distribution are so sharply defined; but 
careful tabulation of similar facts in regard to others would 
prove equally interesting and significant. 
If the foregoing facts be carefully considered, one feature is 
sure to attract attention -by reason of its constant reiteration. 
This is the influence apparently exerted by the geologic forma- 
tions upon the distribution of certain classes and species of 
trees, or, for the sake of argument, the coincidence which 
exists between certain geologic formations and certain facts of 
plant distribution. 
From whatever point of view we may regard the matter, it 
finally resolves itself into an examination of the soil condi- 
tions, which are directly dependent upon the structure and com- 
position of the geologic formations from which the soils were 
derived. Soil influence is indicated in all the facts of plant distri- 
bution throughout the state as one of the most potent factors, 
and in some instances as the only one, to be taken into consid- 
eration; and here it seems pertinent to remark that the name 
which any geologic formation may bear is of no consequence 
in this connection, except for purposes of identification. The 
only matter of any moment is its lithological characters, either 
mechanical or chemical, irrespective of age or stratigraphic 
position. A sandy soil, whether a recent dune deposit or one 
formed from the disintegration of Paleozoic sandstone in place, 
would be of equal importance so far as sand-loving plants are 
concerned. In the same way a heavy soil, whether of creta- 
ceous marl or glacial till, might be equally available as a home 
for species which must have such a mechanical condition for 
their proper growth. Those which merely require a rocky soil 
would also be indifferent as to whether the rock was Eozoic 
granite or Triassic trap. 
This line of argument, therefore, infers that the mechanical 
structure of the soil is of equal importance with its chemical 
constitution ; and this is apparently the fact. The observations 
made seem to indicate that the former is the more powerful in 
influencing the original location and distribution of species, 
while the latter more largely affects their subsequent growth. 
Upon this basis of reasoning we may account for the fact that 
