1915] BAILEY & SHEPARD—SANIO’S LAWS 71 
for a species must obviously be based upon a large amount of 
material selected from mature plants grown in different environ- 
ments. However, general averages of this character are of little 
value for the purposes of the systematic botanist, or in the identifica- 
tion of woody tissues, and are only of relative value to the manu- 
facturer of wood pulp. 
Bussey INSTITUTION 
HARVARD UNIVERSITY 
