12 Donald Reddick 



that his conclusions in souk- instances are based on very meager data. 

 It appears from his table 2 thai his biologic form VII is established on a 

 single inoculation of from three to six plants of the test variety. It ap- 

 pears also, from his discussion on pages 5 and 6, that the organisms used 

 varied as much as two years in the time at which they were first brought 

 into artificial culture. While there is no definite information that these 

 races lose virulence in culture, there are inferential data on this point 

 in the experience of those at this institution who have worked with the 

 organisms. Burkholder (1925) has shown a positive case of attenuation 

 in Fusarium martii f. sp. phaseoli, and the phenomenon is well known 

 in the case of many bacterial parasites of animals and man. 



The race which has been isolated at Bonn and studied comparatively 

 by Boning (1926) corresponds most nearly with the beta race. Bu1 if 

 the Leach formula is applied, it would appear that the Bonn race is dis- 

 tinct. Boning says (page 8 of reference cited) : "Von den 14 in Amerika 

 widerstandsfahigen Sorten miissen 2 als sehr anfallig gegentiber dem 

 hiesigen Pilzstamm gelten, 1 weitere werden, wenn auch nur in geringem 

 Grade, befallen, wahrend die ubrigen 8 Sorten auch wohl unter hiesigen 

 Verba' 1 1 n issen widerstandsf ahig sind. ' ' 



Although it seems somewhat unlikely (owing to the number of cases), 

 there is, of course, the possibility that the seed which Boning obtained 

 for his tests is not of the same varieties as were used by Barrus or Burk- 

 holder. Such mistakes in naming varieties are not uncommon, and, as 

 is well known, different varieties are sometimes offered for sale under 

 the same name. Furthermore, the condition described by Salaman 

 (1926), for potato, may well apply in the case of beans. He records 1 

 that a newly introduced variety occurs in England which is partly im- 

 mune and partly susceptible to the wart disease. Such a condition ac- 

 tually existed in the hybrids reported here before they were sorted for 

 susceptibility to the gamma race. 



Obviously, one of the next things to do is to make tests with all of the 

 known races of Collet otrichum lindemuthianum. Even then, however, 

 one could never be sure that a new race might not appear at any moment 

 from some variety of beans which might be brought into a given locality. 

 Such an event might be expected in the case of garden varieties, where 

 novelties are being introduced almost yearly by a large number of seeds- 

 men. In the case of field beans, however, the tendency seems to be in the 

 other direction. Fewer varieties of staples are desired, in order that 

 standardization may be effected. It is very unlikely that a new variety 



1 "It has happened within the writer's knowledge, that a newly introduced variety fof 

 potato] consisted in reality of the product of two seedlings so much alike that no dif- 

 ferentiating- externa] features wnich would serve to distinguish them could he found, 

 and yet one seedling was immune and the other susceotible to Wart Disease." — Sala- 

 man (1926:16). 



