rious
curtailment of crop.

Yet in this very department of hers Nature has for ages hidden away what
has been disclosed within twenty years as one of her least suspected
marvels. It is no other than that certain parasites of field and meadow
so far from being hurtful, are well worth cultivating for the good they
do. For a long time the men who devoted themselves to the study of peas,
beans, clovers, and other plants of the pulse family, were confronted
with a riddle they could not solve. These plants all manage to enrich
themselves with compounds of nitrogen, which make them particularly
valuable as food, and these compounds often exist in a degree far
exceeding the rate at which their nitrogen comes out of the soil. And
this while they have no direct means of seizing upon the nitrogen
contained in its great reservoir--the atmosphere. Upon certain roots of
beans and peas it was noted that there were little round excrescences
about the size of a small pin's head. These excrescences on examination
with a microscope proved to be swarming with bacteria of minute
dimensions. Further investigation abundantly showed that these little
guests paid a handsome price for their board and lodging--while they
subsisted in part on the juices of their host they passed into the bean
or pea certain valuable compounds of nitrogen which they built from
common air. At the Columbian Exposition, of 1893, one of the striking
exhibits in the Agricultural Building set this forth in detail. Vials
were shown containing these tiny subterranean aids to the farmer, and
large photographs showed in natural size the vast increase of crop due
to the farmer's taking bacteria into partnership. To-day these little
organisms are cultivated of set purpose, and quest is being made for
similar bacteria suitable to be harnessed in producing wheat, corn, and
other harvests.

These are times when men of science are discontented with mere
observation. They wish to pass from watching things as nature presents
them to putting them into relations wholly new. In 1866 DeBary, a close
observer of lichens, felt confident that a lichen was not the simple
growth it seems, but a combination of fungus and algae. This opinion, so
much opposed to honoured tradition, was scouted, but not for long.
Before many months had passed Stahl took known algae, and upon them sowed
a known fungus, the result was a known lichen! The fungus turns out to
be no other than a slave-driver that c