362 Joiirnal of Agricultural Research voi. xv, no.6 



storage are not universally followed and not necessarily trusted by every- 

 one. We have occasionally found sweet potatoes stored with Irish 

 potatoes and in cellars with cabbage, turnips, and other root crops for 

 which a low temperature was required. In the South most of the sweet 

 potatoes are stored in earth banks, and often when these are opened a 

 considerable percentage of all of the crop is found decayed. The pota- 

 toes about the edges and on top in some of these banks are frozen, indi- 

 cating that probably the entire lot had been exposed to a low temperature 

 perhaps for a considerable length of time. Furthermore, sweet potatoes 

 are taken from storage during the winter and shipped distances requiring 

 from 3 to 1 2 days or more for them to reach the market. Since most of 

 these shipments are to the northern and eastern markets, they may be, 

 and frequently are, subjected to a low, if not freezing, temperature. 

 After reaching the terminals they may be subjected to lower temperatures 

 for a considerably longer period by the usual methods of handling. An 

 examiiiation of such material showed that they often arrive in bad condi- 

 tion. Many of the potatoes are rotted or partially so and unsalable. A 

 study of such material, as well as material taken from cellars and Irish 

 potato storage houses, shows that they are not decayed by Rhizopus 

 nigricans and some of the other well-known storage-rot fungi, but by some 

 of the forms discussed above, requiring low temperatures, as, for example, 

 Mucor racemosus or Botrytis cinerea. So, bearing in mind the fact that 

 sweet potatoes, even in storage, during transportation, and at the termi- 

 nals may be subjected to the temperatures suited to some of these forms, 

 it will be readily understood that the loss caused by these organisms may 

 be considerable. Moisture is, of course, essential for those forms which 

 are so much in evidence at low temperatures. In the banks there is little, 

 if any, provision made for the escape of moisture. In cellars and in 

 storage houses designed primarily for other purposes it is inadequately 

 provided for. Sweet potatoes are generally shipped in barrels or bushel 

 baskets and the moisture may accumulate in car-load shipments, espe- 

 cially if the temperature is low. The optimum comditions for some of 

 these fungi are, therefore, unavoidably provided. 



The facts presented as to the specific requirements of various fungi in 

 general are not new. Link (25) has shown that while both Fusarium 

 oxysporum and F. trichothecioides Wollenw. can produce tuber-rots and wilt 

 of the Irish potato, the optimum temperature of F. oxysporum is higher 

 than that of F. trichothecioides. Similar data has been published by Brooks 

 and Cooley (4), who found from a study of the temperature relations of 

 the apple storage-rots that the optimum temperature requirements of the 

 various fungi differed greatly. Sphaeropsis tnalormn produced no evident 

 rot at 15°, nor did the species of Penicillium and Neofabraea at 10° at the 

 end of a week, while Sclerotinia cinerea produced a measureable rot at 5° 

 in one week and at 0° in two weeks. The optimum temperature of 

 Neofabraea malicorticis was found to be 20°, F. radicicola 30°, all the 



