30 



The establishment and care of shade and ornamental trees is en- 

 tirely different from the care of forest trees. Knowledge concern- 

 ing the life-history of trees in general is, however, a prerequisite for 

 the proper treatment of both classes of trees, but the art by which 

 this knowledge is applied is entirely different. The forester grows 

 trees to harvest and at harvest time he aims to obtain from them 

 as much and as high grade wood as possible. The tree warden grows 

 trees to preserve. He aims to develop a tree with as desirable an 

 appearance as possible and to retain it as long as the vitality of 

 the tree will permit. 



Thousands of dollars are spent annually by shade and park com- 

 missions in developing the aesthetic side of our cities, towns, and 

 many of our rural districts. The commissions or individuals w^ho 

 have this in charge, aim, by beautifying the environments, not only 

 to improve the health and efficiency of the citizens, but also to raise 

 their moral standard and hence increase their social worth. 



DECIDUOUS AND EVERGREEN TREES. 



All trees native to the State of Pennsylvania, when in a healthy 

 condition, bear green foliage in summer. In autumn many of the 

 green leaves change to brilliant colors, yellow, scarlet, deep red, or 

 purple, and gradually fall to the ground. The species of trees whose 

 leaves lose their green color and fall in autumn are known as 

 deciduous trees. Most of the trees native to the State of Pennsyl- 

 vania are deciduous. The deciduous trees are also known as hard- 

 woods or broad-leaf trees. The Oaks, Maples, Birches, and Chest- 

 nut are common examples of this group. Many of the representa- 

 tives in this group yield valuable products and furnish interesting 

 objects of study on account of their variation in form. In winter 

 the deciduous trees are far more conspicuous than in summer since 

 the dense leaf canopy is absent. This affords an opportunity to 

 study the trees with special reference to their form, branching, and 

 bark. These characters are among the most helpful in distinguish- 

 ing our common trees, especially since they are at hand at all sea- 

 sons of the year. The leaves of a few deciduous species like the 

 Beech and some of the Oaks die in autumn but often persist through 

 the winter. 



Some species, however, do not shed all of their leaves in fall. Such 

 trees are know^n as evergreen trees. The evergreen habit is char- 

 acteristic for most trees commonly known as conifers. Most of 

 the conifers have needle-shaped leaves which persist for two or more 

 years. The Larch, native- to this State, and the introduced Bald Cy- 

 press are, however, two species which shed all their leaves in fall and 

 during the winter appear like dead conifers. The persistence of the 



