170 TREES OF THE NORTHERN UNITED STATES 
7. Pépulus nigra, L. (BLACK PopuaR.) 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. 
P, nigra. Occasionally planted. 
From Europe. 
8. Pépulus balsamifera, L. (BALSAM- 
POPLAR. TACAMAHAC. BALM OF GILEAD.) 
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). 
CLASS II. GYMNOSPERM 2. 
Plants in which the pistil is represented by an open 
seale instead of a body with a closed ovary, as in Class I. 
OrpER XLI. CONIFER. (Pine Fatty.) 
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, 
