22 PRACTICAL COURSE IN BOTANY 
EXPERIMENT 20. THE USE OF ADHESIVE FRUITS. — Scatter broadcast 
a handful of hooked or prickly seeds or fruits — cocklebur, tickseed, beggar- 
ticks, bur grass, etc. Are they suited for wind transportation? Drop one 
of them on your sleeve, or on the coat of a fellow student; will it stay 
there? What would be the effect if it became attached to the fur of a 
roaming animal? Is this a successful mode of dissemination ? 
31 
Fias. 30-32. —30, A pod of wild vetch, with mature valves twisting spirally to 
discharge the seed ; 31, pod of crane’s-bill discharging its seed ; 32, capsules of witch- 
hazel exploding. 
19. Agencies of dispersal.— The means at nature’s dis- 
posal for this purpose, as shown by the experiments just made, 
are four; namely, wind, water, the explosion of capsules due 
to the withdrawal of water, and the agency of animals, in- 
cluding man. The first three are purely mechanical. The 
Fias. 33-36. — Fruits adapted to wind dispersal : 33, winged pod of pennycress ; 
oe spikelet of broom sedge; 35, akene of Canada thistle ; 36, head of rolling spin- 
ifex grass. 
last, animal agency, is either voluntary or involuntary, ac- 
cording as it is conscious and intentional, or accidental merely. 
Man, of course, is the only consciously voluntary agent. Of 
