394 
SOME GENERAL PLANT PROBLEMS 
3. Rejuvenation of Worn-out Land. — In the eastern part 
of the United States there are many farms which have been 
abandoned because the soil has become so poor that there 
is no profit in the crops raised. This condition has come 
about gradually by taking crops off, year after year, without 
replacing food material 
for succeeding crops. 
Fertility can be restored 
by supplying proper ferti¬ 
lizers and by the rotation 
of crops some of which 
must be leguminous. (See 
page 257.) 
323. Conservation of 
Wild Flowers.—The main 
reason for the study of 
fungal diseases, plant 
breeding, and the general 
problem of conservation 
outlined in this chapter 
is their economic impor¬ 
tance to man. From time 
to time in the discussion 
of animals and plants in 
the previous pages of this 
book, your attention has 
been called to facts about 
living things without any 
thought of their direct eco¬ 
nomic bearing. In each 
instance we have been trying to give you a clearer under¬ 
standing of how animals and plants live, in the hope that 
some of this information will give you pleasure in the future. 
It would be a poor course in biology that did not emphasize 
the pleasure which knowing our wild flowers gives all lovers 
Figure 360. — Hepatica. 
One of the earliest wild flowers, and 
one of the greatest favorites. It should 
be left growing in its natural surround¬ 
ings, and not transplanted as a common 
practice is. Only a part of the blossoms 
should be picked from each bunch, in 
order that some may be left to mature 
and scatter seed. 
