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No. 385.] FORESTRY AND GEOLOGY. 13 
includes a great diversity of soil and climate. It is doubtful 
whether the sand barrens in many localities could ever be 
reforested by deciduous trees after the complete destruction 
of the pines. Certainly many such areas have remained com- 
pletely devoid of any growth for many years, whereas in the 
deciduous zone clearings quickly become reforested, often by 
pines and cedars which were not before to be found in the 
region. i 
When the soil characters of each zone are studied, it becomes 
easy to understand why the character of the vegetation in each 
is so different. In the deciduous zone the rocks are partially 
weathered and disintegrated for a considerable depth, and this 
disintegration is unceasingly going on, constantly adding new 
material to the soil from the variety of the mineral constituents 
in the rocks. New soil is constantly being made and the old 
soil being renovated, so that plant food is in process of manu- 
facture all the time. The character is also such that it is 
capable of retaining moisture for a considerable period, which is 
a valuable factor in periods of drought. 
On the other hand, in the coniferous zone the rock has long 
been almost completely disintegrated, and as it is practically 
composed of but one constituent, quartz, which is of little or 
no value for plant food, any further disintegration is incapable 
of yielding any other element, and but little is added to the 
soil which could serve to support vegetation.' Further than 
this, in many places no rock disintegration is going on, but, on 
the contrary, rock is in actual process of formation. Sand- 
stones and conglomerates are being formed by cementation 
with limonite, and where this occurs, a hard layer results which 
limits the downward growth of roots, while if the conditions 
are such that an open porous sandy soil prevails, it becomes 
impossible for water to be retained in it, and an arid sand 
barren is the result. 
The logical conclusion is that if the flora of the coniferous 
zone should be destroyed, its reéstablishment in the zone would 
be a very difficult matter on account of the hostile physical 
conditions which are ceaselessly at work there; while in the 
deciduous zone its struggle for existence, even if it gained a 
