34 GRIGGS: OBSERVATIONS ON THE BEHAVIOR 
flower freely but fruit sparingly either because of faulty fertiliza- 
tion or because of a short season; conditions while adequate for 
adult plants may be unfavorable for the development of seedlings. 
To determine how far these various possibilities restrict the spread 
of the plants under consideration they have been classified accord- 
ing to the apparent success of the reproductive system as follows: 
Fic. 4. Unifolium canadense at Sugar Grove. Beds as thick as this are rare in 
this region. Although flowering freely, the plant does not fruit well 
REPRODUCTION OF SPECIES ON THE EDGES OF THEIR RANGES 
Flowering scantily 
Gaultheria procumbens* Pyrola elliptica* 
Isotria verticillata Pyrola rotundifolia*® 
Passiflora lutea Sambucus pubens*t 
Phlox stolonifera*t Stylosanthes biflora 
Fruiting sparingly although flowering freely 
Aesculus spas Lysimachia quadrifolia 
Asclepias variegata Napaea dioica 
Blephariglottis lacera Quercus minor 
Diospyros virginian Rubus odoratus. 
Lycopodium Iwctduto porophilum§ — U ‘nifolium canadense 
* Fruit appears to’ set’’ and mature werk: 
T Species confined to aa southern portion of the area. 
t Species confined to the northern portion of the area. 
§ Sporangia comparatively scarce 
{ Dioecious, only one plant found. 
