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BULLETIN OF WISCO'SIX NATURAL HISTORY SOCIETY. VOL. 2. NO. 1. 
suffer an individual dwarfing, so that such a tree, although but a 
few feet high, may be a hundred years old. 
The results which appear to flow from the above observations 
are the following: 
I. The occurrence of more or less xerophytic species of Viola 
in a given locality depends on the amount and quality of humus 
in the soil. 2. Scantiness of humus favors specific adaptations for 
reducing transpiration, but does not diminish the vigor of growth ; 
sourness of the humus tends to produce dwarfishness both of the 
whole plant and its separate parts. 
The case of Viola obliqua growing in a sedge marsh, as men- 
tioned above, does not necessarily militate against the second con- 
clusion. It is by no means uncommon to find colonies of a species 
in a station not at all adapted to its growth. But such colonies are 
apt to be transitory ; the numbers and individual vigor of the mem- 
bers is likely to diminish with each generation, until they dis- 
appear. I am unable to state how long V. obliqua has been in the 
marsh in question, but it will be interesting to watch its future 
history. It is probable that it will gradually disappear, unless 
the marsh should dry up and its soil become less sour; or unless 
the invaders should develop a variation which would adapt it to 
the new conditions. 
