Family Convolvulaceae 183 



aides should be converted into trap-doors of two pairs, 

 at least i}4 feet wide, opening by means of weights 

 either way from the center, and occupying the entire 

 length. 



A series of roof ventilators should be provided, 

 sufficient to cany oflE at least most of the moisture. 

 In small houses there should be at least two such 

 ventilators, each about three feet square and about 

 five feet high. In medium sized houses there shovild 

 be three of similar dimensions. In large houses 

 from four to six ventilators shotild be provided 

 (fig. 29 a andc). 



Where sweet potatoes are stored in bins, they 

 should first be put into every other one, beginning 

 with the lowest and finishing with the top floor. 

 Thus the filled bins wiU have a chance to dry out. 

 Bins deeper than seven feet should be divided by two 

 partitions, leaving a two or three inch air space 

 betw^ai them. The inner bins throughout should be 

 filled first. It is a mistaJce to close doors and venti- 

 lators when the potatoes are sweating, for during this 

 stage aU the ventilation possible should be given, even 

 at night, provided of course that the temperature 

 does not go so low as to cause chiUing. 



Artificial Aids in Storage: Each floor should be 

 provided with an accurate recording thermometer and 

 hygrometer. With the hdp of these two instru- 

 ments, the critical point of excess heat and moisture 

 may be easily determined. It is possible that in order 

 to bridge over these critical periods in storage some 

 system of artificial 6xy\ng may be required. This 



