22 BULLETIN 204, U. S. DEPARTMENT OF AGEICULTUEE. 



some species has been favored in situations quite unsuited to their 

 requirements. This is particularly true in the case of the oaks and 

 gray birch. These species constitute a very large proportion of the 

 deciduous growth of the region and are very susceptible to gipsy- 

 moth attack. On a great deal of the area now covered by these 

 species the white pine would grow to much better advantage, would 

 yield a much more valuable product, and if pure, or nearly so, would 

 prove immune to gipsy-moth attack. The white pine reproduces 

 itself readily under favorable conditions, and is already fairly 

 abundant in numerous localities. For these reasons the white pine 

 recommends itself very strongly as a substitute for the existing moth- 

 susceptible species, and this species has been considered to a very 

 large extent by this department in its experiments to create a safe 

 stand of timber. The deciduous species which are of value and im- 

 mune to gipsy-moth attack require most favorable situations for 

 their profitable development, and such situations are very few and of 

 small area. An exception in the case of chestnut may be made in 

 this connection. This is a valuable tree and one well suited to grow 

 over a considerable area. Its growth is not recommended on account 

 of its susceptibility to the widespread and fatal chestnut blight. But, 

 like the red oak, it may be found possible to grow it satisfactorily in 

 small numbers with other species. 



EXPERIMENTAL WORK. 



The experimental work has been conducted by means of small 

 areas known as "sample plats." These vary in size from one-half 

 an acre to 6 acres and occur both scattered and grouped in different 

 parts of the infested region. They are necessarily located on the 

 lands of private owners who are willing to submit their lands to this 

 use. 



An effort has been made to distribute this work as widely as pos- 

 sible over the infested region. (PL IX.) In this way the greatest 

 variety of conditions is encountered and the results are available to 

 the greatest number of woodland owners. Each sample plat varies 

 from another in one or more of the following points: Composition of 

 stand, age of stand, degree of infestation, and method of treatment. 

 Each sample plot generally consists of two parts. One of these is 

 the portion upon which actual experimental work is done and the 

 other serves as a control or check plat. Upon the latter nothing 

 whatever is done, as its purpose is to provide a means of comparing 

 results under natural and artificial conditions. The corners and 

 boundaries of all plats have been plainly marked, and the areas 

 surveyed and mapped. All trees 1 inch and over in diameter have 

 been calipered on each plat and control, and the measurements 

 recorded. Forest descriptions of each plat have been written. 



