52 
SEED DISPERSAL. 
Fig. 40. — Ripe fruit of pin 
clover, or Alfilerilla, 
ready to twist into fleeces 
of sheep or into loose soil. 
bearded point down, sticking into the soil. The first rain 
or heavy dew straightens out the awns, which are twisted 
again as they dry. The bearded point works a little 
farther with each change, and after twisting and untwist- 
ing a number of times it gets 
down three or four inches into the 
sand, often to moisture, where 
the awns decay and the grain 
germinates. Here is an admi- 
rable scheme for moving about 
and for boring into the ground. But this is not all. 
The grains are quick to catch fast to clothing, as 
people move among the plants, and they are ad- 
mirably fitted for attaching themselves to dogs and 
sheep, which they annoy very much. These animals 
transport the grains for long distances. The twist- 
” ing and untwisting of the awns enable the grain to 
bore through the fleeces, and even to penetrate the skins 
and make wounds which sometimes cause the death of the 
animal. Examine also seeds of pin clover, Alfilerilla, 
which is becoming abundant in many parts of the world. 
33. Winged fruits and seeds fall with a whirl. — The 
large fruit of the silver maple falls in summer. „ As these 
trees are most abundant along the margins of streams, 
the fruit often drops into the water and is carried down 
stream to some sand drift or into the mud, where more 
sand is likely to cover them. Thus sown and planted 
and watered, they soon grow and new trees spring up. 
