inds of seeds.--Ants are numerous, strong,
skillful, and in suitable weather are always very busy. Their habits
have been investigated, and it has been found that in some respects
they are genuine farmers on a small scale. They have their slaves
(not hired help); they feed their plant lice, remove them from place
to place, and otherwise care for them, because the lice constitute
one of the chief sources of their supply of sweet. They build roads
and houses, and enjoy society after their fashion. They have use for
certain kinds of seeds, portions or all of which they eat at once
or carry to their homes. A number of persons in different countries
and at different times have seen ants carrying seeds. Some young
student of botany may have noticed along one side of the glossy seeds
of the bloodroot a delicate, fleshy ridge, and wondered what could
be its use. The answer can now be given with a good degree of confidence.
The ants either eat this fleshy ridge at once, or, as more frequently
happens, carry such seeds to their homes. The smooth seeds they do
not eat, but cast them out of their nests after using the part they
like; after being rejected the seed may stand a chance to germinate.
The seeds cannot be carried so well unless this ridge, _caruncle_,
be present. Other seeds of this nature are those of wild ginger,
celandine, cyclamen, violet, periwinkle, some euphorbias, bellwort,
trillium, prickly poppy, dutchman's breeches, squirrel-corn,
several species of Corydalis, Seneca snakeroot, and other species
of milkworts.

[Illustration: FIG. 52.--Seed of bloodroot with caruncle or crest,
which serves as a handle for ants to hold on to. Ant ready to take
the seed.]

[Illustration: FIG. 53.--A view of a seed of euphorbia with a soft
bunch at one end, a handle for ants.]

In his work on _Vegetable Mold and Earthworms_, p. 113, Darwin states
that earthworms are in the habit of lining their holes, using seeds
among other things, and that these sometimes grow. In this way the
worms aid in spreading plants.

43. Cattle carry away living plants and seeds.--In Arizona, where
cacti abound, Professor Toumey finds that many of them are broken
in pieces by cattle, which eat a portion, while other portions often
adhere to the legs or noses and are carried from place to place. These
fragments are usually capable of growing.

The unicorn plant, _Martynia proboscidia_, common in the
southwestern portion of the United States, is some