8 Donald Heddtck 



lion on the susceptible varieties. The season was very satisfactory for 

 elimination of mosaic, but anthracnose never became abundant. Green- 

 house tests were continued immediately after the field harvest. Xo crop 

 was grown in 1924. In 1925 the following field notation was made : 

 "Very heavy infection eventually resulted and by the end of the season 

 the test could be called the most severe to which the hybrids ever have 

 been subjected." A similar notation was made for the season of 1926, 

 with the addition that the cold and wet summer gave valuable informa- 

 tion on the behavior of the late-maturing varieties and on the relation of 

 determinate and indeterminate growth to staining, mold, rot, and prema- 

 ture growth of seed. 



CONCLUSIONS 



The evidence presented above has been summarized from a mass of 

 notes and records covering seven years. There seems to be no occasion 

 to publish the notes in detail, but they will be preserved and may be 

 consulted by any one who cares to see them. When it is borne in mind 

 that for all practical purposes four separate and distinct diseases are 

 involved in the work, it appears that material progress in building up 

 resistance to diseases in common field beans has been made. 



The relative ease with which the work has been done indicates that 

 this method of attacking the whole problem of disease control in plants 

 gives promise of a condition of permanent control which deserves the 

 widest attention. That other investigators are coming to a similar con- 

 clusion is obvious from a perusal of disease-control literature of the past 

 decade, and more particularly of the past five years. Considering the 

 enormously successful results obtained in the classical examples of per- 

 manent control of disease — the European control of Phylloxera of the 

 grape by the use of resistant stocks, the control of wilt disease of cotton, 

 cowpea, and other plants by hybridization with a resistant parent, and 

 so forth — it is a matter of surprise that even more attention has not been 

 given to this method. 



It is not to be concluded at all that the hybrids developed in this work 

 will go at once into commercial production and eventually replace the 

 present sorts. Some of the problems remaining to be considered are 

 discussed in succeeding pages. In the meantime, however, any worker 

 who desires samples of these hybrids may have them in small quantity 

 for any further work along this line that he cares to undertake. 



DISCUSSION 



So far as the introduction into commerce of any of these particular 

 hybrids is concerned, there are certain very definite things that remain 

 to be found out. 



