72 BICKNELL: FERNS AND FLOWERING PLANTS OF NANTUCKET 
velop an occasional weak Spine. In other more variable charac- 
ters the plant is also noteworthy. The leaves are often smaller 
and thicker than in the typical form with the larger veins distinctly 
impressed above; they may also be duller green in color, less 
deeply cleft, less sharply dentate and with more obtuse lobes. 
Parts of the stem and branches are often densely bristly but, by 
the exfoliation of the pale outer bark, become bright reddish 
brown and wholly unarmed except for the infra-axillary spines. 
This form of the plant is the prevailing one on Nantucket. 
The typical plant also occurs and each form appears to shade in- 
sensibly into the other. 
Many specimens of the pubescent form are identical with typi- 
cal material of Aibes oxyacanthoides, var. calcicola Fernald, from 
the Province of Quebec (Rhodora '7: 153-155. Au 1905). 
