and darts are blown by the wind. Berries have their seeds dropped
afar by birds. Aquatic plants and those that grow beside running
water travel by river and flood. European species reach our
shores among the ballast. Darwin raised over sixty wild plants
from seed carried in a pellet of mud taken from the leg of a
partridge. So on and so on. The imagination delights to picture
these floral vagabonds, each with its own clever method of
getting a fresh start in the world. But by none of these methods
just mentioned do the tick-trefoils spread abroad. Theirs is
indeed a by hook or by crook system. The scalloped, jointed pod,
where the seeds lie concealed, has minute crooked bristles, which
catch in the clothing of man or beast, so that every herd of
sheep, every dog, every man, woman, or child who passes through a
patch of trefoils gives them a lift. After a walk through the
woods and lanes of late summer and autumn, one's clothes reveal
scores of tramps that have stolen a ride in the hope of being
picked off and dropped amid better conditions in which to rear a
family.

Only the largest bees can easily "explode" the showy
tick-trefoil. A bumblebee alights upon a flower, thrusts his head
under the base of the standard petal, and forces apart the wing
petals with his legs, in order to dislodge them from the
standard. This motion causes the keel, also connected with the
standard, to snap down violently, thus releasing the column
within and sending upward an explosion of pollen on the under
surface of the bee. Here we see the wing petals acting as
triggers to discharge the flower. Depress them and up flies the
fertilizing dust - once. The little gun will not "go off" twice.
No nectar rewards the visitor, which usually is a