OF SOME SPECIES AT THE EDGES OF THEIR RANGES oe 
Fic. 3. A small plant of Epigaea repens in flower at Sugar Grove 
suppose common over much wider areas than is shown by the 
collections. This list includes: 
Andropogon virginicus 
Asplenium pinnatiidum 
Aster divaricatis 
Aruncus Aruncus 
Ascyron multicaule 
Betula nigra 
Castanea dentata ; 
Chimaphila maculata 
Cunilla originoides 
Daystoma laevigata 
Epigaea repens 
Eupatorium coelestinum 
Gaultheria procumbens 
Gyrostachys gracilis 
Hieracium venosum 
Kalmia latifolia 
Lycopodium lucidulum 
Lycopodium complanatum 
Oxydendrum arboreum 
Pinus rigida 
Pinus virginiana 
Pyrola elliptica 
Quercus Prinus 
Saxifraga virginiensis 
Sericocar pus asteroides 
Solidago bicolor 
Tsuga canadensis 
If now we attempt to determine by analysis the factors which 
cause the termination of the ranges, our first inquiry is naturally 
concerning the reproductive functions of the plants under dis- 
cussion. It has been supposed, somewhat generally, that the repro- 
ductive functions of many species fail at the northern or southern 
edges of their ranges. The failure may occur at any one of 
several points in the cycle: a plant may not produce flowers in 
sufficient numbers to maintain its place in plant society; it may 
