18 Levi Otto Gratz 



and soil surveys. He concluded from these experiments that all the 

 strains studied by him were the same. These strains were obtained from 

 a wide range of hosts from different parts of the countiy. Peltier observed 

 no marked specialization in any of them. He did note, however, that 

 the virulence of the fungus was extremely variable, as was also the degree 

 of resistance of the various hosts. Growing the strains on artificial media, 

 he observed much variation, those from the same host often producing 

 different growth on the same substratum. However, the variations in 

 cultural characteristics exhibited by isolations from different hosts were 

 no greater than those manifested by two strains from the same host or 

 by the same strain at different ages. Again, he could find no standard 

 for distinguishing the different strains by means of mycelial cell measure- 

 ments, because of the extreme variation in size even in the different isola- 

 tions from the same host. Sherbakoff isolated Corticium vagum from 

 more than fifteen hosts. He used eight strains, isolated from lettuce, 

 castor bean, amaranthus, watermelon, cowpea, the pods of the garden 

 bean and the velvet bean, and tomato fruit, and one culture received 

 from Duggar, to inoculate seedlings of lettuce, celery, eggplant, pepper, 

 and tomato. He found some strains pathogenic on cabbage, cauliflower, 

 cucumber, garden bean, and other hosts, but it is not clear whether the 

 fungus from potato was included in these. He concludes that the strains 

 are morphologically alike, but makes no mention of any specialization 

 in pathogenicity. 



Rosenbaum and Shapovalov (1917), however, reported the isolation of 

 a strain from potato which can be distinguished from the common form 

 by the more pronounced lesions made when the strain is inoculated on 

 injured stems or tubers; by the reaction, growth, and character of sclerotia 

 on artificial media; and morphologically, by measurement of the diameter 

 of germ tubes when the short, or " barrel-shaped," cells, enveloping the 

 sclerotia, are placed in drops of water to germinate. 



Edson and Shapovalov (1918) reported extreme variation in patho- 

 genicity of the Corticium vagum strains used, from those absolutely unable 

 to attack any underground parts to those which produced large and deep 

 cankers. Also, not only were the size andthe depth of the lesions consistently 

 unlike, but their color and shape were consistently rather peculiar to certain 

 individual strains. These investigators found that the strains in no way 

 had become attenuated by reason of growth on artificial media for long 

 periods. One in particular was very aggressive, being strongly parasitic 

 on tomatoes and sugar beets, both as a damping-off fungus and in pro- 

 ducing a root rot of adult plants. 



Finally, the work of Matsumoto (1921), which is the most comprehensive 

 and the most recent, must be considered. Fifteen isolations were obtained 

 from different localities, from potato, lettuce, eggplant, Habenaria sp., 

 and navy bean, and one from an unknown source. These were studied 



