June 1941] Agricultural Research in New Hampshire 31 



insect. For these experiments, the investigators developed an ap- 

 paratus consisting of multiple units in a constant temperature and 

 constant humidity cabinet. 



It was found that methyl alcohol exhibits a more rapid and ex- 

 tensive penetration than any of the other alcohols in the series used. 

 A low boiling petroleum derivative gave a more rapid and extensive 

 penetration than a fraction somewhat higher in boiling range. It 

 seems possible that the ability of a liquid to dissolve the epicuticle of 

 an insect, which is of a waxy nature, may influence the rate and 

 amount of penetration through the integument. Interesting specula- 

 tions also revolve around the question of size of molecule. The de- 

 tailed results of these investigations were published in Technical 

 Bulletin 74, "Penetration of Certain Liquids Through the Pronotum 

 of the American Roach," No. XIV of the series "Studies of Contact 

 Insecticides." 



The latter half of 1940 was devoted to the development of a de- 

 vice (insect toximeter) for securing uniform application of liquids 

 to all surfaces of test insects. The "insect toximeter" utilizes a turn- 

 table of controlled variable speeds, on which is mounted a device for 

 holding a series of insects, each in a similar but separate position. 

 The spray materials are delivered from two air brushes mounted in 

 such a way that the two columns of mist meet at the turn-table and 

 thereby give a uniform coating to all the insects in the experiment. 

 The entire apparatus is mounted within a housing which prevents 

 stray air currents or eddies. An exhaust fan removes the spray mist 

 from the housing at the close of each experiment. 



Utilizing this apparatus, an extensive series of studies are un- 

 derway. They are designed to establish the relationship between 

 variations in concentration of a given toxicant and variation in the 

 number of seconds during which the toxicant is applied. They are 

 also designed to establish the median lethal dose of materials which 

 can serve as standards, including c.p. rotenone, nicotine, and the 

 pyrethrins derived from pyrethrum flowers. 



(Purnell Fund) 



FORESTRY 



Plantation Studies (C. L. Stevens) 



The objective of this study is to determine what species of trees, 

 both native and introduced, are best adapted to artificial reforestation 

 in New Hampshire. Seedlings are raised in the nursey and set out 

 on college-owned land. At intervals the plantations are visited, ex- 

 amined, and measured. The measurements of older plantations have 

 been continued, and are now nearly complete. 



Measurements of recent plantations of white and red pine show 

 an average survival of 91 per cent in the 1938 area, and 96.5 per cent 

 in the 1939 area. Small plots of exotic species planted in the arbore- 

 tum in 1939 have not shown satisfactory results. Conifers average 

 60 per cent survival and hardwoods 84 per cent. 



In the fall of 1940 approximately 3 acres of land were seeded 



