170 



TREES OF THE NORTHERN UNITED STATES 



7. P6pulus nlgra, L. (BLACK POPLAR. ) Leaves 

 rather large, deltoid, pointed, serrate with glan- 

 dular teeth, smooth on both sides even when young. 

 Leafstalk somewhat compressed. Buds very 

 sticky. A very variable, large (50 to 80 ft. high), 

 rapidly growing tree with spreading branches. 

 Occasionally planted. 

 From Europe. 



8. P6pulus balsamifera, L. (BALSAM- 

 POPLAR. TACAMAHAC. BALMOFGILEAD.) 

 Leaves very large, ovate, gradually acu- 

 minate, sometimes heart-shaped, finely 

 serrate, smooth, bright green above, 

 whitened beneath; leafstalk nearly round; 

 leaves in spring rich yellow. Branches 

 ridged below the leaves ; buds large and 

 covered with very fragrant resin. A me- 

 dium-sized tree, 40 to 70 ft. high, py- 

 ramidal in form. Wild in the North and 

 often cultivated. 



Var. candicans, or Balm of Gilead, has 

 larger and more or less heart-shaped 

 leaves (the larger figure in the cut). 



P. balsamifera. 



CLASS II. 



Plants in which the pistil is represented by an open 

 scale instead of a body with a closed ovary, as in Class I. 



ORDER XLJ. CONlFER-ffi. (PINE FAMILY.) 



As far as the number of species is concerned, this is 

 the largest order of trees and shrubs of temperate and 

 cold-temperate regions. The order is of the greatest im- 

 portance, both on account of the valuable timber it fur- 

 nishes and for its resinous secretions, turpentine and resin. 



