Nov. II, 1918 Sweet-Potato Storage-Rots 363 



other fungi 25°. The range of optimum temperature requirements for 

 apple-rot fungi is even greater than for the storage-rot fungi of the sweet 

 potato. That cool weather is required for infection of the Irish potato 

 by the lateblight fungus, Phytophthora infesians, is well known. On the 

 other hand, Gilman {11) concludes that relative high temperatures are 

 required for infection of cabbage by F. conglutinans and Tisdale (38) 

 arrives at similar conclusions for the infection of flax by F. lint. Other 

 references might be made to show that the various fungi have different 

 temperature requirements. On this point no generalizations can be made. 



OTHER FUNGI ISOLATED AND STUDIED 



A considerable number of other fungi, mostly species of Fusarium 

 has been isolated and studied — namely, F. hatatatis Wollenw., F. hyper- 

 oxysporum Wollenw., F. radicicola Wollenw., F. caudatum Wollenw., 

 F. solani (Mart.) Sacc, F. incarnatum (Rob.) Sacc, F. orthoceras Appel 

 and Wollenw., F. orthoceras var. triseptatum Wollenw., F. oxysporum 

 Schlect., Nectria ipomoeae Hals., and an undetermined species of Mucor. 

 These fungi have all been subjected to the same tests of parasitism as 

 those classed as storage-rot organisms. 



Preliminary experiments were conducted in which sweet potatoes 

 were inoculated at the end or in some wound and then confined in a 

 moist chamber, both wrapped and not wrapped in moist filter paper and 

 then in oiled paper. They were inoculated by wounding and then dipped 

 in spore suspensions and confined in moist chambers but without result. 

 Chilling the potatoes by exposing them to cold-storage temperatures 

 (2.0° C.) for a week and then inoculating in the usual way did not yield 

 results. Soaking in water before inoculation was without effect. A 

 large number of sweet potatoes have been inoculated, after which they 

 were divided up into several lots and exposed to the temperatures of the 

 different chambers of the Altmann thermostat. In no case were the 

 results consistent enough to warrant the conclusion that any of these 

 organisms would cause decay at the temperatures used. 



Fusarium hatatatis and F. hyper oxysporum are the two species well 

 known as the cause of stemrot (2^) of sweet potatoes. These two organ- 

 isms frequently invade the fibrovascular bundles of the roots, often 

 extending entirely through the potato. To know whether these organ- 

 isms caused storage-rots is of considerable importance in view of their 

 prevalence and destructiveness to certain varieties in some parts of the 

 country. Roots naturally infected have been gathered and stored in 

 bushel baskets in the storage houses with the other potatoes, and in every 

 case they kept just as well as healthy potatoes. Naturally infected roots, 

 after a thorough washing, have been wrapped in wet filter paper and 

 then in oiled paper and subjected to the temperatures of the different 

 chambers of the Altmann thermostat. Not in a single chamber did any 

 of the potatoes rot. The writers conclude from these results that these 



