THE BLACK POPLARS. 25 



two parents. It will be noticed that this new hybrid is a cross 

 between two poplars belonging to different sections of the genus. 

 Populus generosa, Henry, was first described in Gardeners' 

 Chronicle, Ivi. 258 (17th October 1914); but the reader's 

 attention may be drawn to the account of this and other artificial 

 hybrids, which has been published in Journal of Department of 

 Agriculture, Ireland, xv. 44, fig. 6 (October 19 14). Populus 

 generosa is easily propagated by cuttings, and will shortly be on 

 sale at a trade nursery, where the valuable P. robusta also is 

 obtainable. 



The following Key, together with Figs. 11 and 12, reproduced 

 from Trees of Great Britain, vol. vii. t. 409 (191 3) will serve for 

 the discrimination, by the leaves and twigs, of the various 

 poplars mentioned above. The black poplars constitute the 

 section Aigeiros, Duby in De CandoUe, Syn. PL Fl. Gall. i. 427 

 (1828), and are distinguished from the other groups (aspens, 

 white poplars, balsam poplars, etc.) by their leaves, green on 

 both surfaces and bordered with a clearly defined translucent 

 margin. 



KEY TO THE BLACK POPLARS. 



L — Leaves never ciliate in margin. 



1. Populus mgra, Linnccus. Wild in Europe, Caucasus, Siberia. 



Leaves rhomboid, about 3 inches long, 2 inches broad, cuneate at the 

 base, gradually tapering above into a long acuminate apex ; glands never 

 present on the base. Stigmas 2. Stamens 15 to 30. 



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



The Lombardy poplar (var. italica) is the fastigiate sport of var. typica , 

 and var. plantierensis is the fastigiate sport of var. betulifolia. 



II. — Leaves ciliate in margin. 



* Glands absent on the base of the leaf. 



2. Populus Freinontii, Watson. Wild in California, Utah, Texas. 



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

 base ; on old trees deltoid with a truncate base ; about 2i inches wide ; apex 

 cuspidate ; serrations few, coarse, incurved. Stigmas 3. Stamens about 60. 



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



3. Populus deltoidea, Marshall, var. monilifera, Henry, in Gardeners' 

 Chronicle, Ivi. 2 (4th July 1914). 



[Populus vioniltf era, Aiton.] 



Twigs rounded. Leaves deltoid-ovate, about 3 inches wide, shallowly 

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



