150 MASS. EXPERIMENT STATION BULLETIN 170. 



to a particular location or habitat, it has realized its optimum condition 

 for development. In some cases there is reason to believe that their 

 choice may be determined by some minor inherent peculiarity common 

 to the species, such as seed habit. 



Some species of plants are confined to dry soils, while in other loca- 

 tions the same species grow in moist situations. In a botanical sense 

 these are identical species, but they may possess such different physiolog- 

 ical adaptations as to warrant the term " physiological species." 



Soil texture plays an important role in the distribution and develop- 

 ment of plants, and is inseparably associated with water-retaining capacity. 

 Soil texture affects the color, size and 'thickness of the foliage, and also 

 has an influence upon susceptibility and nonsusceptibility to certain 

 troubles. 



Even in limited areas trees possess different habits of growth, and soil 

 texture is probably the most important contributory factor. For example, 

 the elms in the eastern part of Massachusetts are different from those in 

 the Connecticut valley. Those growing in the Housatonic valley differ 

 from either, assuming a more vase-like form and being characterized 

 by the development of a larger number of vertical leaders or branches. 

 The greatest number of symmetrical elms and the best types of branch- 

 ing occur in this region. 



The rock maples in the Connecticut valley are of a different type from 

 those found elsewhere, growing larger and more luxuriantly. This region 

 is characterized, also, by the occasional occurrence of a beautiful, dark- 

 colored, densely foliaged form resembling the black maple, Acer sac- 

 charum var. nigrum, noticed farther west. Like the elm, much difference 

 in the branching habits of the rock maple may be observed here and 

 there which appears to be characteristic of certain localities. 



There is, however, a wide diversity of conditions in nature under which 

 trees may live and develop. The rock maple, oak and hickory appear to 

 be at home on our rocky hillsides, while the basswood, canoe birch and 

 beech are adapted to soil containing humus. The chestnut is confined 

 largely to clay hills or "drumlins," where it has grown since time im- 

 memorial. The sycamore, pin oak, red maple, tupelo and swamp white 

 oak are confined to low, moist soil ; while the scarlet, red, white and yellow 

 oaks, pitch pine, poplar, gray birch and red cedar prefer drier locations. 

 The willows, Carolina poplar, red birch and hackberry are closely re- 

 stricted to streams; and the white cedar, tamarack and black spruce to 

 swamps. The white pine is quite generally distributed, and in New 

 England it is adapted to a greater variety of conditions than any other 

 tree in our flora. 



Notwithstanding the wide diversity of conditions to which our native 

 trees are subject, they can with care be made to thrive under different 

 conditions. Rhododendrons may be grown successfully in dry soil having 

 2 or 3 feet of muck placed underneath, and trees adapted to moist places 

 will develop well in poor soil if freely supplied with fine-textured loam. 



