THE MONTHLY BULLETIN. 



CALIFORNIA STATE COMMISSION OF HORTICULTURE 

 Vol. VI. February, 1917. No. 2 





SOME OBSERVATIONS UPON THE RELATION OF 

 HUMIDITY TO THE RIPENING AND 



STORAGE OF FRUITS. V/V 



By A. 1). Siiamel, TJ. S. Department of Agriculture. 



For the past three years, 1914 to 1916, inclusive, the writer, in cooper- 

 ation with Mr. Frank F. Chase of Riverside, California, has made some 

 observations of the effect of different conditions of relative humidity 

 upon the ripening and curing of lemons held in storage. 



The experiments have been conducted in the National Orange Com- 

 pany s Lemon storage and packing house at Corona, California. In this 

 building there are twenty rooms, each containing about 8,000 cubic feet 

 of space. These rooms are insulated by means of a four-inch filling of 

 pine shavings between galvanized iron walls. Beneath each room is a 

 basement. The floors of the rooms over the basement are made of 

 pieces of wooden two by fours arranged with cracks between them about 

 one-half inch wide. In the basements of live of the rooms steam 

 radiators have been provided, connected with an outside heating plant, 

 so that the temperature of the air in the rooms can be raised to a 

 maximum of about 135 degrees Fahrenheit. Ventilating doors have 

 been arranged in the lower outside walls of the rooms and in the upper 

 inside walls, in such positions that the air in the rooms can be quickly 

 changed when desired. Special humidifiers have been provided for 

 raising the relative humidity of the rooms when needed, so as to main- 

 tain, with ventilation, any condition desired. While the insulation of 

 tin' rooms has been found to be imperfect, a reasonably effective control 

 of Hie conditions of temperature and relative humidity has been secured 

 by means of ventilation, steam heat and the special humidifiers. 



In an experimental curing of a roomful of lemons, with the room 

 maintained for four weeks at about 90 degrees Fahrenheit and about 

 90 per cent relative humidity, more than 90 per cent of the cut stems 

 of the fruits calloused over perfectly in the same manner as is some- 

 times the case with cuttings under favorable conditions. While this 

 condition had been observed before in isolated cases of lemons cured 

 under good storage conditions, it was the first time, in the writer's 

 knowledge, where any such large proportion of the fruits developed this 



callous. 



In fuil her experiments, where the rooms of lemons were held at 

 differenl temperatures and different conditions of relative humidity, it 

 was discovered that the development of the calloused condition depended 

 ■ largely on the maintenance of a uniform condition of relative humidity. 

 It was also found in these experiments that the callous developed more 

 rapidly under a high temperature of about 95 degrees Fahrenheit, 

 than under a low temperature of about GO degrees Fahrenheit. It was 

 demonstrated that under fluctuating conditions of relative humidity, 



