324 GENERAL PLANT PATHOLOGY 



the cement,, and destroy such expensive filling work. Most ornamental 

 and shade trees having only a few dead limbs are unquestionably worth 

 attention. Others which have many dead limbs, or numerous decayed ' 

 areas may not be worth the expense. Trees of large size, rare trees, 

 historic trees and trees which fill a peculiar place in the landscape are 

 probably worth saving by the most expensive methods of tree surgery, 

 if necessary. Another phase of tree surgery is the commercial side, 

 where ignorant men and tree fakers have undertaken to make a business 

 of pruning and treating trees. The sad appearance of excessively 

 pruned trees in all of our large American cities are living spectacles of 

 the zeal of such men, who should be driven out of the business, as they 

 have in Philadelphia by the municipal authorities undertaking to do 

 the work by the employment of skilled tree surgeons. 



Bailey, L. H.: The Pruning Book. The Macmillan Co., New York, 1907. 

 Blakeslee, Albert F. and Jarvis, Chester Deacon: Trees in Winter. Their 



Study Planting Care and Identification. The Macmillan Co., New York, 1913. 

 Collins, J. Franklin: Practical Tree Surgery. Yearbook of the United States 



Department of Agriculture, 1913 : 163-190. 

 Gaskili, Alfred: The Planting and Care of Shade Trees. 



Forest Park Reservation Commission of New Jersey, 191 2, with papers on Insects 



Injurious to Shade Trees by John B. Smith and Diseases of Shade and Forest 



Trees by Mel T. Cook. 

 Start, E. A. Stone, G. E., and Fernald, H. T.: Shade Trees. Bull. 125, Mass. 



Agric. Exper. Sta., Oct. i, 1908. 



It has been a matter of general knowledge that a disease may be 

 controlled by a change in the time of planting, for with smuts the very 

 different climatic conditions prevailing at the time of the various 

 sowings have influenced the rate of infection. Early sowing of winter 

 wheat has been found beneficial in the reduction of the amount of 

 stinking smut, for wheat sown early in October showed no sign of infec- 

 tion, while plants sown at the end of October were much attacked 

 (about 60 per cent.) by the smut. By experiment as a problem in 

 prophylaxis this matter of sowing as a means of controlling disease 

 should be established for all of our important cultivated crops. 



Then too, a study of the cells and tissues which protect plants 

 against the entrance of insects and fungi is a matter of prophylactic 

 interest. The formation of cork, of bark, of callus, of how in response 

 to the attack of fungi, the multiplication of protecting, or outer cells, 

 is accomplished, should receive the attention of the student of phyto- 



