PLANT BREEDING 323 
of Agriculture in this direction have been the production 
of a disease-resisting variety of Sea Island cotton and of 
watermelons. The soil of valuable cotton plantations had 
become infested with a fungus (Fusarium), which attacked 
the roots of the plants, plugged the vessels with its hyphae, 
and destroyed almost the entire crop. In consequence of 
this many planters gave up cotton-growing. Observation 
showed that often in a field where nearly all the plants 
were killed here and there an individual survived, blos- 
somed, and ripened its capsules. For four years plants 
were bred from the seeds of these resistant individuals 
until a variety was secured which withstood the attacks 
of the fungus and made it possible to resume cotton- 
growing on the abandoned plantations. 
Extensive areas in the South, once devoted to the culture 
of watermelons, became so infected by a fungus (Fusarium) 
that melon-growing was no longer possible. The destruc- 
tion was so complete that no process of selection could be 
adopted, as in the case of the cotton. It was, however, 
found that the roots of the so-called “citron,” a plant of 
the watermelon genus, were not attacked by the fungus. 
Watermelons were hybridized with “citrons,” and about 
a thousand varieties were grown from the seeds thus ob- 
tained. Many of.these proved resistant, but only one was 
found to be resistant and at the same time desirable in 
most other respects. This one variety is now grown with 
perfect success on any fungus-infected soil. 
