OP THE WASATCH REGION 11 



2. POPUL.US. Poplar; Cotton wood; Aspen. 



Trees, often of excurrent habit, and with brittle branches. 

 Buds scaly, covered with a resinous varnish. Leaves leathery. 

 Flowers in catkins appearing before the leaves; long and 

 drooping. Stamens many. 



Petioles flattened laterally. 



Styles 2; terminal buds small, but slightly resinous- 

 viscid. 



Mature leaves smooth on both sides.. 1. P. tremuluides 

 Mature leaves becoming smooth above; white- 



tomentose below 2. P. alba 



Styles 2-4; terminal buds large and very resinous- 

 viscid. 

 Leaves truncate at base. 



Branches spreading 3. P. deltoides 



Branches erect 4. P. nlgrra 



Petioles terete or channeled; not laterally flattened. 



Leaves broadly ovate 5. P. eandlcans 



Leaves lanceolate or lanceolate-ovate. 



Leaves acute, short-petioled 6. P. angustifolla 



Leaves acuminate, long-petioled 7. P. acuminata 



1. P. tremuloides Michx. Quaking Asp; American Aspen. 

 A slender tree with smooth, light-green branches. Leaves 

 broadly ovate or roundish, short-acuminate; margin crenulate 

 and ciliate; moving with the slightest breeze. Mountain 

 slopes, usually at altitudes of 7,000-9,000 ft. in the Great Basin. 

 March -May. 



2. P. alba L. White or Silver-leaved Poplar. A large tree 

 in moist climates, but seldom exceeding 75 ft. in the Great 

 Basin. Branches smooth, covered with a white bloom; the 

 trunk light-green. Leaves broadly ovate or roundish, palmately 

 3-5-lobed or merely coarsely dentate; petioles shorter than the 

 blade, sometimes scarcely flattened. Catkins greenish. Sta- 

 mens 6-20. Cultivated. March-May. 



3. P. deltoides Marsh. (P. monilifera Ait.) Carolina or 

 Necklace Poplar. The largest tree of the genus; with grayish - 

 green bark, becoming rough when old. Leaves glabrous; 

 broadly ovate-triangular; abruptly acuminate at apex; crenu- 

 late; truncate at base; petioles stout. Bracts glabrous, deeply 

 fringed. Stamens 60 or more. Pistillate catkins loosely- 

 flowered, becoming 6-10 inches- long in fruit. Capsules on 

 slender pedicels. Cultivated. April-May. 



4. P. iiiyra L. Black Poplar; Lombardy Poplar. Tall trees 

 usually with excurrent trunks, sometimes reaching a height 

 of 100 ft. Leaves broadly deltoid with an abruptly acuminate 

 apex and a crenate margin; obtuse or broadly wedge-shaped 

 at the base. Staminate catkins 1-2 inches long; stamens 

 about 20 to each flower. Pistillate catkins 2-5 inches long, 

 spreading. Capsule very obtuse, on pedicels much shorter 

 than capsule. Cultivated. April-May. 



5. P. candicans Ait. (P. balsamifera candicans (Ait.) Gray.) 

 Balm of Gilead. A large much -branched tree (20-90 ft. high) 

 with large very resinous terminal buds. Leaves broad, more 

 or less heart-shaped; their lower surfaces and the petioles 

 hairy. Styles 2-4, with dilated lobes. Cultivated. April. 



