SHADE TREES. 



133 



of China, is often termed the "tree of heaven," concerning which Dr. 

 Asa Gray has well remarked that its blossoms are "redolent of anything 

 hut airs from heaven." To obviate the disagreeable odors arising from 

 this species only the pistillate trees should be used for planting, the dis- 

 agreeable odor being given off by the male or staminate flowers, which 

 are often borne on separate trees. The Ailanthus apparently tolerates 

 obnoxious atmospheric gases better than most other trees. 



TULIP TREE (Liriodendron tulipifcra). This is an excellent tree for 

 roadsides, although it is not very much planted. It is probably better 



Fn;. 7. Avenue of pin oaks transplanted seven years in 40 foot avenue. 



suited to lawns and country streets than to the hard usage it might receive 

 on city streets. The tulip is indigenous to different parts of New England. 

 It is a difficult tree to transplant successfully, and this may account for 

 its not having been more extensively employed. This species attains a 

 large size, developing a large symmetrical crown with -handsome foliage. 

 It requires good, well-drained soil, and is best adapted to wide avenues 

 provided with generous tree belts. The leaves sometimes become badly 

 spotted from attacks of insects and fungi, but the loss in transplanting 

 and its lack of adaptability to certain situations are the chief objections 

 to its use as a street tree, at least in the north. 



WHITE ASH (Fraxinus americana). This ash is commonly seen on 

 streets. It was formerly planted more extensively than at present. Our 

 measurements of a number of white ash trees which had grown in good 



