78 THE HUMAN SIDE OF PLANTS 
it travels in the fall! Very true are the poet’s 
words: 
“A primrose by the river’s brim, 
A yellow primrose was to him— 
And it was nothing more!” 
There are plants which can tie sailor’s knots! 
The Virginia knotweed was skilled in this art long 
before man had even heard of it. The knotweed 
is a first cousin to the common knot-grass, and also 
to the prince’s-feather. The tiny flowers of the 
knotweed are held on a long, club-like stalk, at the 
base of which is a joint, that well represents a sail- 
or’s knot. When the seeds of this plant are ripe, 
the pods containing them, which form the knots, dry 
rapidly and shrink. As this shrinking continues, 
the knot at last yields to the strain and snaps apart 
—hurling the seeds out and away, to germinate in 
places far from the parent plant. This action is 
much like the motion of the small boy with his 
sling-shot. 
The capsules of several of the violets have a 
strange, mechanical movement of the valves by 
means of which they actually shoot their seeds, often 
to a distance of several inches from the parent 
plant. While the seeds are ripening, the pod droops 
its head until it is hidden beneath the leaves; but, 
as soon as the seeds are fully developed and ready 
