PLAXT 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 hyphse, 

 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 

 untH 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. 



