Abele 



167 



Californian tree; leaves short-acuminate, truncate 6r reniform 



at base. 

 Southwestern tree; leaves mostly long-acuminate, more or less 

 broadly wedge-shaped at base. 

 Bract at the base of the pistillate flower small, appressed. 



Young leaves pubescent; fruits nearly sessile; European intro- 

 duced trees. 

 Branches spreading. 

 Branches erect. 

 Leaves glabrous; capsules slender-pedicelled; native trees. 

 Leaves crenulate; pedicels as long as capsules or longer; 



eastern tree. 

 Leaves coarsely crenate; pedicels shorter than capsules; western 

 tree. 

 Leaves broadly ovate to suborbicular; stigma-lobes filiform. 

 Leaves coarsely sinuate-dentate. 

 Leaves crenulate-denticulate to entire-margined. 



Petioles mostly longer than the blades; leaves mostly glandless. 

 Petioles about as long as the blades; leaves thick, 2-glandular on 

 the under side at the base of the blade. 



10. P. Fremonti. 



11. P. mexicana. 



12. P. nigra. 



13. P. italica. 



14. P. delloides. 



15. P. Sargentii. 



16. P. grandidenlaia. 



17. P. iremuloides. 



18. P. cercidiphylla. 



I. ABELE — Populus alba Linnseus 



This tree, known also as White poplar and Silver-leaf poplar, from the white- 

 velvety under surfaces of its leaves, is a 

 native of Europe and Asia, but has been 

 much planted in eastern North America, 

 and, as it suckers very freely, has passed 

 in many locaUties beyond the limits of cul- 

 tivation, in yards and along roads, from 

 New Brunswick to Ontario and Virginia. 

 It sometimes becomes 30 meters high, with 

 a trunk a meter or more in diameter. 

 The bark is^ light gray and nearly smooth, 

 or much roughened, with brown blotches, 

 dark brown and rough or fissured toward 

 the base of old trunks. The young twigs 

 are purplish and white-downy, becoming 

 smooth and gray. The buds are 5 to 6 

 mm. long, downy, ovoid, pointed. The 

 young leaves are very densely' white-vel- Fig. 122. — Abele. 



vety, their upper surfaces becoming dark green and smooth; when mature they 

 are 6 to 10 cm. long, lobed or irregularly coarsely toothed, broadly ovate to nearly 

 orbicular in outline, pointed, firm in texture, the base rounded or somewhat heart- 

 shaped, the lower surface becoming smooth or remaining more or less velvety; the 

 roundish leaf-stalks are shorter than the blades. The flowers appear before the 



