28 GRIGGS: OBSERVATIONS ON THE BEHAVIOR 
minations of the specialist are dependable. These must be 
eliminated from consideration by plant geographers because no 
reliance can be placed on the various local lists which must form, 
in large measure, the basis of such work. Lastly there is a very 
large and at present increasing number of plants, the very specific 
identity of which is not yet understood. These include numerous 
recently recognized species and some older ones which have not 
been sufficiently studied. The difficulties occasioned by these 
deficiencies in our knowledge have limited the work very con- 
siderably and because of them I have sought to illustrate my points 
as far as possible with such well-known and conspicuous species 
as Kalmia latifolia and Rhododendron maximum, which are collected 
and listed by every amateur botanist. 
The first question that arises concerning the behavior of a 
species at the edge of its range is as to its abundance. Do the 
individual plants become scarcer and scarcer until finally the 
species fails altogether, or is it common close up to the edge where 
it suddenly stops short? The species whose ranges terminate in 
the Sugar Grove area are therefore classified from this point of 
view in the following table. 
ABUNDANCE OF SPECIES ON THE EDGES OF THEIR RANGES 
Piants common in many stations 
Andropogon virginicus 
Aralia spinosa* 
Aruncus Aruncus 
Ascyron hy pericoides' 
Asplenium pinnatifidum 
Aster divaricatus 
Betula lutea* 
Betula nigra* 
Carex costellata 
Cassia nictitans 
Chrysosplenium americanum 
Circaea alpi 
Cornus stolonifera (abundant at Columbus 
eas 
Cunilla originoides - 
Cypripedium acaule 
Das 
igata 
Dentaria heterophylla* 
Diospyros schipcinyg 
papas repen. 
Eupatorium eouaaica 
Hydrangea arborescens 
Isopyrum biternatumt 
Juncoides saltuensis 
Kalmia ig 
Koellia 
Lechea AS 
nd 
Panicum cara 
