198 HORTICULTURE FOR SCHOOLS 



and 1922, the latter in 1894, found by bitter experience by 

 how narrow a margin of temperature these trees are kept 

 alive. The cold was so severe that a large part of the crop 

 was ruined and, in many instances, the trees were killed to 

 the ground. Had the thermometer dropped a few degrees 

 lower in either case, the industry in the states concerned 

 would have been very largely wiped out. 



The danger from frost is ever present. The orange will 

 stand a temperature of 25 degrees without serious damage, 

 but the lemon will be injured rather badly. Elaborate pre- 

 cautions have to be taken, therefore, in the way of orchard 

 heating; and it is no uncommon sight in the citrus district, 

 during the early morning hours of December, January, and 

 February, to see the fires burning in thousands of orchard 

 heaters of every imaginable type. Some varieties of Navel 

 oranges .are more susceptible to injury by frost than are 

 others; and it is hoped that in the course of time more re- 

 sistant forms will be developed which will retain the good 

 qualities of the cultivated orange of today. 



289. Marketing. The marketing of citrus fruit has 

 always been a perplexing problem. The greater part of the 

 crop is shipped hundreds, in many cases, thousands of miles, 

 and it has been necessary to devise an elaborate system of 

 refrigerator-car service so that the fruit can be kept cool 

 from the time it leaves the packing-house until the boxes are 

 removed from the car in some distant part of the country. 



Frequently the fruit colors before it tastes sweet and the 

 United States Government and the cooperative marketing 

 organizations, working together, have attempted to protect 

 the consumer by insisting on a standard of sweetness which 

 would be satisfactory to the person eating the fruit. The 

 method by which this standard was established is known as 

 the eight-to-one test. The fruit is considered ripe when there 

 are eight parts of soluble solids in the fruit to each part of 

 acid. The soluble solids are for the most part sugars, and 



