Family Convolvulaceae 183 



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

 at least ijA 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 carry off 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 should 

 be three of similar dimensions. In large houses 

 from four to six ventilators should be provided 

 (fig. 29 a and c). 



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 will 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 

 between them. The inner bins throughout should be 

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

 lators when the potatoes are sweating, for during this 

 stage all the ventilation possible should be given, even 

 at night, provided of course that the temperature 

 does not go so low as to cause chilling. 



Artificial Aids in Storage. Each floor should be 

 provided with an accurate recording thermometer and 

 hygrometer. With the help 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 drying may be required. This 



