PLANTS THAT ARE CARRIED BY ANIMALS. 73 
ber of fruits, and even the upper fruit-bearing branches, 
have sticky glands with which to catch on to any passing 
object. Among these are some kinds of sedges, chick- 
weeds, and catchflies. 
The sticky substance on seeds and fruits not unfre- 
quently serves another good turn besides enabling them 
to adhere to animals. The slime holds them to 
the spot where they are to grow, or it enables 
some to float or to sink in water, according to 
the amount of .the mucilage. 
46. Three devices of Virginia knotweed. — A 
perennial plant, four to five feet high, grows on 
low land, usually in the shade. 
It is Polygonum Virginicum, 
and so far without a common 
name, unless Virginia knotweed 
be satisfactory. It is a near 
relative of knot grass and smart- 
weed and Prince’s feather. The 
small flowers are borne on a 
Inner and ratlipv stiff FlG 55 -~ Frait of Virginia knotweed 
long, eiasuc, ana raxner s mi ready t0 sh00t off when sliakenj or 
stem, and each flower stalk has tolet g0 of stera and catch on to 
' passing animal. 
a joint just at the base. As 
this fruit matures, the joint becomes very easy to separate. 
It dries with a tension, so that, if touched, the fruit goes 
with a snap and a bound for several feet. The shaking 
produced by the wind jostling several against each other 
is sufficient to send off a number of ripe fruits in every 
