22 CALIFORNIA FRUITS: HOW TO GROW THEM 



of our fruits, and that is the low percentage of humidity which our 

 atmosphere contains. In California the percentage of humidity is 

 high in the winter and low in the summer ; in the East the condi- 

 tion is just reversed. For this reason summer heat is far more 

 oppressive in the East than in California, and for the same reason 

 certain serious fungoid diseases which prevail at the East, though 

 found here in less injurious degree directly on the coast, may be 

 wholly unknown in the interior where the air is drier. The dry air 

 also favors the access and action of light and heat, for Tyndall says 

 that a sheet of vapor acts as a screen to the earth, being in a great 

 measure impervious to heat. 



It is not necessary, then, that there should be clouds to lessen the 

 chemical effects of sun heat in fruit ripening. Not only do clouds 

 intercept sunshine, but water vapor in the air when to the eve the 

 sun is bright as ever can absorb a large quantity of the effective 

 sun rays, and so retard fruit ripening. Hence an apparently sunny 

 country which has much invisible water vapor in the air, may prove 

 defective in fruit-ripening qualities. 



It is true that air free from humidity allows rapid escape of heat 

 by radiation as well as free access of it, and in dry air frost is more 

 severe, but at the time of the greatest fruit growth, from June to 

 October, radiation down to a frost point is prevented by other natural 

 agencies. In the early spring and late autumn the humidity per- 

 centage rises again and checks radiation just at the time of the year 

 when it is most desirable to have it checked. 



The accompanying table, compiled from the records of the United 

 States Weather Bureau, shows the prevailing relative humidity in the 

 East and South and in California. 



Normal Relative Humidity at Eastern and California Points 



Galveston, Tex 84.6 78.0 79.3 77.4 78.1 77.2 75.6 80.4 78.5 



California Stations 



Los Angeles 73.1 75.2 73.0 75.4 76.2 72.9 74.3 66.6 73.3 



Fresno 59.3 52.7 42.4 " 34.7 34.7 43.6 55.1 64.1 48.3 



Sacramento 67.6 67.6 66.1 59.8 59.8 59.0 62.4 66.8 63.6 



Red Bluff . ..61.9 56.8 43.7 35.6 35.3 43.6 51.6 60.7 48.8 



THE THREE POINTS COMBINED 



The three great advantages of the California climate abundant 

 heat, continuous sunshine, and dry air taken in connection with 

 the fitness of the soil and the great length of the growing season, 

 insure the characteristic excellence of California fruit, and the early 



