48 
FOURTEENTH REPORT. 
On pine land such as association persisted for a number of years, altho 
ultimately it would be replaced by other associations. Where this has 
not already happened, frequent tires are the cause, for they easily kill 
the small seedlings. As pine must be reestablish by seeds, this very 
materially increases the time from pine to pine as each tire depletes the 
soil in addition to killing the seeds, seedlings and seeding trees. 
Normally aspen dominance of hardwood land was much shorter, both 
because the hardwoods seed easier and sprouts from the stumps often 
obviate seeding entirely. This results in vegetation of a mixtur of hard- 
woods and aspens, with occasionally more or less pine. Ultimately, how- 
ever. if the soil is favorable, the entire stand will be hardwood. 
On bog land aspen dominance was very seldom attained, because 
ecesis of the bog trees was easy and they could much more than hold 
their own against aspens. After a burn in the cedar bog, revegetation 
was very largely by tamarack (Larix hiricina), altho this tree is but 
sparingly represented in a typical cedar bog. The tamarack grows 
readily and forms a dense stand which may reach a bight of about 
55 feet. Soon, however, cedar (Thuja occidentalis ) and spruce ( Picca 
mariuna) appeared and developt rapidly. From a distance such bogs 
appear to be pure tamarack, until either the tamarack dies naturally, 
or is killed by the larvae of Ihe sawfly, or is overtopt by the spruce 
and cedar. The cedar bog is the climatic type on boggy soil. 
THE VEGETATION. 
As vegetation is seldom in a static condition, the treatment of the 
plant associations according to their arrangement in the developmental 
or genetic series is the most logical. This method does not signify 
that every given spot of bare ground becomes vegetated by ihe lowest 
members of its normal genetic series and the succession continues until 
the climatic type for the region becomes prevalent. In a normal genetic 
series such would be the case. Expressing series of fenomena in this 
manner leads to a clearer insight over the whole field and to a clearer 
explanation of apparent exceptions. A genetic series begins with the 
lower types of vegetation and proceeds progressively to higher types. 
A complete series would be the one in which every step was taken, but 
this is frequently not the case. Sometimes steps may be omitted and 
certain steps may take very much longer than others. In spite of these 
facts, the general trend of the vegetation is from the lower steps of 
the genetic series to the higher and the varying environmental factors 
and accidents are largely responsible for the actual steps. 
In this region there are five distinct genetic series. Of these, four 
are primary series, that is, the natural series that represent the vegeta 
tional dynamics without the interference of man, and one, the burn 
series, for which man is directly responsible. The primary series may 
be designated: (1) the lake series, whose associations progress from 
deeper water up to the land; (2) the swamp series, whose associations 
in this region replace open water with swamp vegetation (of relatively 
minor importance in this region) ; (3) the bog series, whose associations 
convert open water into a tree-covered tract; and (4) the sandy -land 
series, whose associations lead towards the development of hardwood 
forest. Anv one of these series may run into some of the others. 
