130 Journal of Agricultural Research voi. xviii. No. 3 



parasite. Of those who report such attempts Wolf (20) may be men- 

 tioned. He inoculated various legume seeds by stirring in a small quantity 

 of water containing a macerated vigorous culture of S. rolfsii. The inoc- 

 ulated seed was then planted in the greenhouse, in a soil which was pre- 

 viously treated with formaldehyde. As a result of this treatment posi- 

 tive infections were obtained with some of the legumes used. Positive 

 infections with 5. rolfsii on pepper plants were also recorded by Fulton, 



In order to establish definitely the pathogenicity of Sderotium roflsii^ 

 and also to determine whether or not there existed varietal or physio- 

 logical strains in this organism, the inoculations reported in Table II 

 were carried out. All hosts were covered with bell jars for 24 hours 

 immediately after inoculation. All inoculations were performed in the 

 greenhouse. 



Although many more inoculations have been made than are reported 

 in Table II, these will show that Schlerotium rolfsii is an active parasite. 



A study of Table II shows further that there are no varietal 

 or physiological strains in this organism, A strain isolated from 

 tomatoes, for instance, will infect a large number of other hosts. 

 This is also true when a strain from a cantaloupe is isolated. Table II 

 also shows that no infection whatsoever could be obtained with a test 

 tube culture i year old, even though the same was mixed with sterilized 

 soil where it had no competition with any other of the soil floras and 

 where it had plenty of available food. However, just as soon as a transfer 

 was made from the i -year-old culture it revived and assumed its normal 

 virulence. It was then in no way different from a fresh strain of Sdero- 

 tium rolfsii recently isolated from a normally infected plant in the field. 



Sderotium rolfsii is truly parasitic, since it is not always necessary to 

 produce infection through puncture inoculations. As shown in Table II, 

 positive infections were obtained when a pure culture of the fungus was 

 merely worked into the soil where moisture was present. These same 

 observations were also reported by Fulton (4). However, Harter (8, 9) 

 could not obtain any infection on Colocasia esculenta or Xanthosom,a sagi- 

 tijolium unless inoculations were made by means of a puncture. The 

 writer has had similar experiences in his inoculations with the Irish and 

 sweet potatoes (PI. 5, B, C) as well as the orange and the apple. In 

 these cases infections were possible only through a wound. On the other 

 hand, however, as soon as infection took and the rot had progressed 

 sufficiently all that was necessary then to infect a healthy tuber of Irish 

 potatoes was to place the latter in close proximity to the former and 

 infection would result without the aid of a puncture. In this case, 

 apparently, the fungus assumed added vigor on the first inoculated tuber 

 and was therefore capable of penetrating the other without the aid of a 

 wound. In Colocasia and Xanthosoma the corms are protected by hard 

 scales, and infection becomes possible only by means of a wound. 



