40 
SEED DISPERSAL. 
grow on the tops of the highest branches, and hold on 
into winter or longer. The stems are about two inches 
long, and soon after drying, 
through the action of the 
winds, they become very 
flexible, each resembling a 
cluster of tough strings. The 
slightest breeze moves them, 
and they bob around against 
each other and the small 
branches in an odd sort of 
way. After so much threshing 
that they can hold no longer, 
the little nuts become loosened 
and begin to drop off a few at 
a time. Certain birds eat a 
few and loosen others, which 
escape. The illustration shows 
some of these nuts, each sup- 
plied with a ring of bristles 
about the base, which acts as 
a parachute to permit the wind 
the easier to carry them for 
some distance before falling, 
or to drift them on the surface 
of the snow or ice. 
23. Seeds that tempt the wind by spreading their sails. 
■ On low lands in the cool, temperate climate of Europe, 
Fig. 29. — (a) Lax stem, supporting ( b ) 
fruit of the buttonwood, or syca- 
more ; ( c ) a single fruit separated, 
ready for the wind or water. 
