Populus I 773 



A. Leaves never ciliate in margin. 



9. Populus nigra, Linnaeus. Europe, Caucasus, Siberia. See p. 1795. 



Leaves rhomboid, about 3 in. long, 2 in. broad, cuneate at the base, 

 gradually tapering above into a long acuminate apex ; glands never present at 

 the base. Stigmas always two. Stamens fifteen to thirty, purple. 



Branchlets and petioles glabrous in var. typica, pubescent in var. betulifolia. 

 The Lombardy poplar (p. 1798) is the fastigiate form of var. typica ; and var. 

 plantierensis (p. 1802) is the fastigiate form of var. betulifolia. 



B. Leaves ciliate in margin. 



* Glands absent at the base of the leaf. 



10. Populus Fremontii, Watson. North America. Seep. 1794. 



Leaves on young cultivated trees, reniform or rhombic, with a cuneate base ; 

 on old trees deltoid with a truncate base ; about 2\ in. wide ; apex cuspidate ; 

 serrations few, coarse, and incurved. Stigmas three. Stamens about sixty, with 

 dark red anthers. 



* * Glands always present on the base of the leaf. 



11. Populus monilifera, Aiton. North America. Seep. 1807. 



Branchlets rounded. Leaves deltoid-ovate, about 3 in. wide, shallowly 

 cordate or truncate at the base, cuspidate at the apex ; serrations sinuate, with 

 incurved tips, fewer and coarser than in the hybrids. Stigmas three or four. 

 Stamens fifty to sixty. 



12. Populus angulata, Aiton. North America. Seep. 18 10. 



Branchlets angled. Leaves triangular-ovate, longer than broad, up to 7 in. 

 long, and 5 in. broad, truncate or cordate at the base, acute or shortly acuminate 

 at the apex. Stigmas four. Stamens fifty to sixty. 



*** Glands variable at the base of the leaf, absent or one or two in number. 



Hybrids between the European P. nigra, and one or other of the American 

 P. monilifera and P. angulata. Leaves with irregular marginal cilia, which are 

 often sparse, and usually deciduous in summer ; serrations not coarse and sinuate. 



* Branchlets glabrous. 



13. Populus serotina, Hartig. Seep. 18 16. 



Branches ascending, wide-spreading. Leaves unfolding latest of all the 

 poplars and with a red tint, ovate-deltoid, about 3 in. wide, with a broad truncate 

 base, and a short cuspidate or acuminate apex. A staminate tree ; stamens 

 twenty to twenty-five. 



14. Populus regenerata, Schneider. See p. 1824. 



Similar to P. Eugenei in habit, with foliage like that of P. serotina, but 

 unfolding a fortnight earlier. A pistillate tree ; stigmas usually only two. 



15. Populus Eugenei, Simon-Louis. See p. 1826. 



A narrow columnar tree, with ascending short branches. Leaves unfolding 

 early with a reddish tint, smaller than those of P. serotina, broadly cuneate at 

 the base, with a slender sharp-pointed non-serrated acuminate apex. A 

 staminate tree ; stamens about twenty. 



VII R 



