INSECTS' AND DISEASES 



85 



stimulabion would always prove advantageous to 

 plants. There appears to be a tendency for electri- 

 cally stimulated plants to develop a more spind- 

 ling growth than those grown 

 under ordinary conditions. 



Conclusions concerning the effect 

 of current electricity on 

 plants. 



In conclusion, it may be 

 stated that the application of 

 electrical stimulation to crops 

 is not as yet practicable, al- 

 though undoubtedly in the future 

 electricity will be more exten- 

 sively employed in agriculture, 

 and it is hoped that agricultur- 

 ists will be able to make use of 

 the enormous amount of electri- 

 cal energy constantly stored in 

 the atmosphere. From the work 

 that has been done, the follow- 

 ing very general conclusions 

 may be drawn : 



(1) Electricity exerts an ap- 

 preciable influence on plants. 



(2) Eilectrical stimulation 

 gives rise to an accelerated ger- 

 mination and growth of plants, 

 the foliage in some instances 

 (radishes) being stimulated more 

 than the roots. 



(3) The strength of current 

 inducing acceleration is confined 

 to a narrow range. 



(4) There is a minimum, opti- 

 mum and maximum stimulus. The minimum cur- 

 rent is equal to about .005 milliamperes, the opti- 

 mum to about .22, and the maximum is determined 

 entirely by conditions. • 



Fig. 



To show 



tbe characteristic 

 grooves on the 

 trunk of an elm 

 tree caused by a 

 feeble stroke of 

 lightning. (Com- 

 pare with Pig. 51. ) 



Literature. 



Some of the literature pertaining to the influence 

 of current electricity on plants is as follows : L. H. 

 Bailey, Electricity and Plant Growth, Transactions, 

 Massachusetts Horticultural Society, Part 1, pp. 54- 

 79, 1894 ; Bertholon, De I'electricite des vSgetaux, 

 Paris, 1783 ; De Candolle, Physiologie vegetale. 

 Tome 3, p. 1088 ; R. Chodat, Quelques effets de 

 I'electricite statique sur la vegetation, Laboratoire 

 de botanique de I'universite de Geneve, Ser. I, 

 Fasc V, p. 53-56 ; Bot. Cen. p. 92, Tome LV ; 

 Gardini, De influxu electrititatis atmosphsericae in 

 vegetantia dissertatio, 1784 ; L. Grandeau, De 

 I'influence de I'electricite atmospherique sur la 

 nutrition des v6getaux, Ann. de Chim. et de Physiq., 

 Ser. 5, XVI, 145-226, Feb., 1879 ; A. S. Kinney. 

 Electro-germination, Bulletin No. 43, Hatch Experi- 

 ment Station, Amherst, Mass., 1897 ; Selim Lem- 

 strom. Electricity in Agriculture and Horticulture, 

 Van Nostrand Company, New York City ; J. Mac- 

 cagno, Ueber den Einfluss der atmosphserischen Elec- 

 tricitat auf das Wachsthum des Weinstocks; Wollny, 

 Forsch. Agricultur-physik, Vol. VI, p. 193, 1883 ; 

 H. M. McLeod, The Effect of Current Electricity on 

 Plant Growth, Transactions and Proceedings New 

 Zealand Institute, XXV, 479-482, May, 1893, 1894 ; 

 the same. Ibid XXVI, 463, 464; N. F. Monahan, The 

 Influence of Atmospherical Electrical Potential on 

 Plants, Sixteenth Annual Report, 1904, Hatch Ex- 

 periment Station ; G. E. Stone, Injuries to Shade 

 Trees from Electricity, Bulletin No. 91, 1893, Hatch 

 Exp. Sta.; G; E. Stone, The Influence of Current 

 Electricity on Plant Growth, Sixteenth Annual 

 Report, 1904, Hatch Exp. Sta.; Stone and Monahan, 

 The Influence of Electrical Potential on the Growth 

 of Plants, Seventeenth Annual Report, 1905, Hatch 

 Exp. Sta.; E. Wollny, Forsch. Agricultur-physik, 

 1882, 1888 ; Ueber die Anwendung der Elektricitat 

 bei der Pflanzenkultur, Miinchen, 1883; Geo. S. 

 Hull, Electro-Horticulture, N. Y., 1898. 



CHAPTER II 



INSECTS AND DISEASES 



' NSECTS AND PLANT DISEASES are the plagues of the husbandman. Their incursions have 

 been deplored from the earliest times, although plant diseases have not long been recognized 

 except under the indeflnite terms of blights and rusts and cankers and mildews. These pests 

 and ailments have entailed endless human labor and have sacrificed numberless animals 

 and crops ; yet the net result has been the enforcing of a more vigorous and constructive 

 agriculture. 



The ailments of plants are constantly becoming more numerous and the knowledge con- 

 nected with them more complex, owing to dissemination of the parasites into new regions, 

 the increase of food supply due to new and more extended cultures, to changes in habits of 

 parasites and hosts conseqiient on the disturbance of the normal equilibrium in nature. At the 

 ' same time, however, the means of contending with these difficulties are increasing with phe- 

 nomenal rapidity. Numbers of persons are now employed at public expense in the study of insects 

 and diseases and in devising means of combating them. This is the guarantee of the future. In fact, 

 our present-day agriculture would be impossible were it not for the entomologists and plant-patholo- 



