382 FUNDAMENTALS OF FRUIT PRODUCTION 



some of them being more reliable in certain districts than others. The pre- 

 dictions for regular Weather Bureau "key" stations, corrected to apply to 

 local conditions are of greatest general use. Several distinct methods of 

 preventing frost have been used in fruit growing sections. The use of 

 smoke screens is of little value in checking the radiation of heat at night. 

 Orchard heating is practicable under certain conditions. However, only a 

 limited protection is afforded by orchard heaters, the exact amount de- 

 pending on the height of the "ceiling layer" of the air, on the number and 

 kind of heaters and on the amount of wind. A protection of 4 or 5°F. on 

 typical frosty nights is all that can be expected under average conditions. 

 Before the installation of orchard heating equipment is warranted there 

 should be reasonable assurance that growing conditions during the average 

 season and the average margin of profit warrant it. Frost occurring 

 after the time of fruit setting may occasionally arrest the further develop- 

 ment of seeds and still permit the fleshy tissues to develop and mature, 

 giving rise to fruits abnormal in size and shape. It may also cause the 

 appearance of "frost rings" or bands of russet around the apical end of 

 the fruit. It occasionally leads to certain other pathological conditions 

 in fruit or foliage. 



Suggested Collateral Reading 



Schimper, A. F. W. Plant Geography upon a Physiological Basis. Pp. 35-51; 



241-259. Oxford, 1903. 

 Chandler, W. H. Hardiness of Peach Buds, Blossoms and Young Fruit as Influenced 



by the Care of the Orchard. Mo. Agr. Exp. Sta. Cir. 31. 1908. 

 Emerson, R. A. Cover Crops for Young Orchards. Nebr. Agr. Exp. Sta. Bui. 92. 



1903. 

 Gladwin, F. E. Winter Injury in Grapes. N. Y. Agr. Exp. Sta. Bui. 433. 1917. 

 Harvey, R. B. Hardening Processes in Plants. Jour. Agr. Res. 15: 2, 1918. 

 Hooker, H. D., Jr. Pentosan Content in Relation to Winter Hardiness. Proc. Am. 



See. Hort. Sci. 17: 204-207. 1920. 

 Macoun, W. T. Overcoming Winter Injury. Proc. Am. Soc. Hort. Sci. Pp. 15-27. 



1908-9. 

 Rosa, J. T., Jr. The Hardening Process in Vegetable Plants. Mo. Agr. Exp. Sta. 



Research Bui. 48. 1921. 

 Selby, A. D. Fall and Early Winter Injuries to Orchard Trees and Shrubbery by 



Freezing. Ohio Agr. Exp. Sta. Bui. 192. 1908. 

 Waite, M. B. Fruit Trees Frozen in 1904. U. S. D. A., Bur. PI. Ind. Bui. 51 (part 



3). 1905. 

 Wiegand, K. M. The Biology of Twigs in Winter. Bot. Gaz. 41: 373. 1906. 



Literature Cited 



1. Abbe, C. U. S. D. A., Weather Bur. No. 342: 168. 1905. 



2. Alter, J. C. U. S. D. A., Mo. Weather Rev. 40: 929. 1912. 



3. Alwood, W. B. Va. Agr. Exp. Sta. Bui. 147. 1903. 



4. Anthony, R. D. N. Y. Agr. Exp. Sta. Bui. 432. 1917. 



5. Augur, P. M. Proc. Am. Pom. Soc. P. 54. 1885. 



6. Baake, A. L. Proc. Am. Soc. Hort. Sci. 17: 279. 1920. 



