BEE PEANTS OF CLAYTON COUNTY 
121 
honey bee or the large bumble bee. The greater length of its 
proboscis permits the small bumble bee to visit corollas having a 
wide range of tube lengths and to effect an entrance to flowers 
more readily than can the honey bee, while it has the advantage 
of more rapid movements than the large, slow moving bumble 
bee, thus enabling it to visit more flowers in period of time 
than the large bumble bee. 
A uniform water supply is essential to copious flower pro- 
duction, on which nectar flow is dependent. Since most mid- 
summer flowers are found in the open forest or prairie, the 
factor light may be regarded as quite as important as water. 
Department oe Botany, 
Iowa State College. 
LITERATURE 
Kemp, J. F,, A Handbook of Rocks, 1911. 
Norton, W. H., Underground Water Resources of Iowa, la. Geol. Survey, 
21 ; 342-358, 1910. 
Schimper, A. F. W., Plant Geography Upon a Physiological Basis, 1903. 
Warming, Eugenius, Oecology of Plants, 1909. 
