MYRICACE^:. 323 



3. .P. tremuloides Mich.: leaves cordate-orbicular, abruptly acuminate, 

 dentate-serrate, pubescent on the margin, green and smooth on both sides. 



Woods. Subarct. Amer. to Penn. April. A tree from 2030 feet high, 

 with smooth bark. Leaves small, light, roundish and slightly cordate. Aments 

 3 4 inches long, pendulous. American Aspen. 



4. P. monilifera Ait. : leaves subcordate-deltoid, acuminate, smooth, 

 with cartilaginous hooked serratures, nearly entire at the base ; petioles 

 compressed above. 



Banks of the Hudson, near Troy, N. Y. and in the western part of that state. 

 W. to Ark. April. A tree 50 $0 feet high, with the younger branches slightly 

 angled. Fertile amenls very long. It seems not to have been found in N. 

 America by either the elder or younger Michaux. Virginian Poplar. 



5. P. nigra yar. betulifolia Torr. ; leaves deltoid-rhomboid, conspicu- 

 ously acuminate, finely crenate-serrate, smooth on both sides. P. Hud- 

 sonica Mich. f. P. nigra, Mich. P. betulifolia Pursh. 



Banks of the Hudson, above Albany. Michaux. March. A tree 30 50 

 feet high, with spreading branches, the younger of which are pubescent. It is 

 probably not a native. According to Loudon, Michaux believed it to be a mere 

 variety .of P. nigra. American Black Poplar. 



6. P. grandidentata Mich. : leaves roundish-ovate, acute, unequally and 

 sinuately toothed, smooth ; white tomentose when young ; petioles com- 

 pressed near the summit. P. trepida Willd. 



var. pendula Nutt. : branches pendulous. 



Woods. Can. to Car. April. A tree 40 50 feet high, covered with smooth 

 greenish bark. Leaves when youmj covered with a thick down, which disap- 

 pears as they become older. The large and unequal indentations on the mar- 

 gins of the leaves sufficiently characterize this species. The variety is found 

 on the Alleghany mountains, Penn. American Large Aspen. 



7. P. lavigata Ait. : younger branches angled ; leaves roundish or del- 

 toid-ovate, acuminate, subcordate, unequally serrate, smooth, glandular at 

 base ; petioles compressed. P. Canadensis Mich. 



Rocky grounds. Can. to Virg. W. to the Rocky Mountains. March. 

 A tree from 70 80 feet high; branches angular, the angles forming whitish 

 lines. Leaves large, deltoid, somewhat cordate ; petioles with two glands at 

 the base. This species has been confounded with P. angulata, but according 

 to the younger Michaux, it is distinct. Cotton Wood. 



8. P. helcrophylla Linn. : leaves roundish-ovate, obtuse, often auricu- 

 lately cordate at base with the sinus small, uncinately toothed, very tomen- 

 tose when young. P. argentea Mich. f. 



Swamps. N. Y. to Car. W. to Miss. May. A tree 4060 feet high, with 

 terete branches. Leaves with lobes or auricles that often ccnceal the insertion 

 of the petiole. Fertile aments about 6 inches in length. 



Various-leaved Poplar. 



ORDER CXYJ. MYRICACE^. GALEWORTS. 



Flowers monoecious or dioecious, amentaceous, naked. STE- 

 KILE FL. Stamens 2 -8, generally in the axil of a scale-like 

 bract. FERTILE FL. Ovary 1 -celled, surrounded by several 

 hypogynous scales ; stigmas 2, subulate or dilated and petaloid. 

 Fruit drupaceous, often covered with waxy secretions. Seed 



