360 Journal of Agricultural Research voi. xv, no. 6 



the different chambers and cultures made. All the potatoes in chamber 

 4 (10.6° C.) were decayed, and F. culmorum was recovered in pure cul- 

 ture. Only 10 per cent were decayed in chambers 5 (13.5° C.) and 7 

 (16.9° C), and F. culmorum was isolated from all. The potatoes in the 

 other chambers and all the controls remained sound. 



F. culmorum produces a distinctively characteristic rot and when 

 once seen would never be confused with any of the other rots except 

 that caused by F. acuminatum, from which it does not differ macro- 

 scopically. The organism decays the sweet potato slowly, requiring 

 three to six weeks to complete its entire destruction. The tissue is 

 rendered spongy but not watery. In the early stages the tissue of the 

 host is a faint reddish brown, which turns later to a carmine-red or 

 maroon. As the potato dries out, some of the deep color is lost, and 

 in the mummified stage it becomes a beautiful pink. 



FUSARIUM ACUMINATUM 



Experiment I. — The method is identical with that used in Experi- 

 ment I of F. culmorum. When these sweet potatoes were removed 

 from storage, all of the treated potatoes and 75 per cent of those not 

 treated were decayed, and F. acuminatum Ell. and Ev. emend. Wollenw. 

 was recovered from each in pure culture. The only other fungi isolated 

 were Mucor racemosus and Mucor sp. 



Experiment II. — ^The method is the same as in Experiment II of 

 Gibberella sauhineiii. When these sweet potatoes were removed from 

 storage, only a small percentage had decayed. F. acuminatum, was 

 recovered from 5 per cent of the treated lot and 17 per cent of those not 

 treated. F. oxysporum was recovered from a few other potatoes. 



Experiment III. — ^The same method was used as that in Experiment 

 III of Gibberella saubinetii. When these sweet potatoes were removed 

 from storage, F. acuminatum was isolated from 75 per cent of the treated 

 and 90 per cent of the untreated. The only other fungi isolated were 

 Mu£or racemosus and a species of Penicillium. 



Experiment IV. — The method was the same as that used in Experi- 

 ment IV of Gibberella saubinetii. All the sweet potatoes were decayed, 

 and F. acuminatum was isolated in pure culture from 95 per cent of both 

 the treated and untreated. Controls were held for all these experiments 

 and while, as might be expected, some of them were decayed, for which 

 several fungi were responsible, F. acuminatum was not isolated from any. 



Trichoderma koningi 



We owe our first knowledge of a storage-rot of sweet potatoes caused 

 by Trichoderma koningi Oud. to Cook and Taubenhaus (8), who found 

 it associated with ringrot and softrot. It probably falls into the class 

 with several other organisms of minor importance which can cause decay 



