14 N. H. AGR. EXPERIMENT STATION [Bulletin 212 



half hour is as injurious to the live tissues of the roots as at an almost immediate 

 drop. 



Some question has been raised by authorities on winter injury with reference 

 to the relation of the size of root to the damage done at a given degree of 

 temperatm-e. WhUe it is obviously true that roots which are several years of 

 age do not suffer as much as younger roots at a given degree of temperature, 

 and it is also true that the older roots are larger than the smaU roots, it may not 

 necessarily follow that considering roots all of the same age the small ones will 

 be found less resistant than the large ones. To test this matter, 500 apple 

 seedlings all of one year of age were carefully tagged, calipered, and a record 

 kept of the average diameter of each. They were then all subjected to a tem- 

 perature of —7.8° C, this temperature being reached after a gradual fall of 

 approximately 1.25° per hour. Records were then made of the per cent of 

 injury to each and a correlation table constructed. 



It was evident that there was no greater tendency for the small roots to be 

 injured than for the large ones. 



The second phase of investigation of this project, the microscopical studies, 

 have not at this time progressed sufficiently so that conclusions may be drawn. 

 A large amount of experimentation was carried on, using different killing fluids, 

 including Fleming's Fluid of various strengths, picro-acetic, chrome-acetic, 

 and Juel's fixatives. A killing fluid is desired which will properly fix the tissues 

 without causing any discoloration that might be mistaken for injury by cold. 



The stains used in the main were simple ones, and some of the best results 

 were obtained from the use of Haidenhain's Haematoxyn contrasted with 

 Orange G. 



A paper giving some of the results on laboratory tests in freezing apple seed- 

 lings was read at the Boston meeting of the American Society for Horticul- 

 tural Science, and further publication of these results is expected within the 

 present fiscal year. 



Root Maggot. 



Since the last report the root maggot studies were concluded. The most 

 important results, including the efficient and practical treatment for the cab- 

 bage root maggot, were published as Technical Bulletin No. 24, "Surface 

 Treatments for the Cabbage Maggot." 



European Com Borer. 



Beginning in the spring of 1922 a new Adams Fund project was started by 

 W. C. O'Kane and P. R. LowTy (Entomology), on the fife history, habits and 

 means of control of the European Corn Borer. Extensive data were secured. 



The work was laid out in consultation with the Bureau of Entomology, of 

 the United States Department of Agriculture, which has been studying this 

 pest under Massachusetts conditions for the last three years. The purpose 

 of the inquiry is to discover accurately the details of the fife history of this 

 new species under New Hampshire conditions. Such knowledge is essential 

 before measures for control can be recotamended. 



A large quantity of corn stalks containing hibernating larvae was secured in 

 Massachusetts and brought to Durham. This furnished material for starting 



