12 
POPULUS 
April. Staminate catkins about 7 or 8 cm. long. Bracts much bigger than in P. nigra. Stamens 
much more numerous (about 60) than in P. nigra. Pistillate catkins pendulous, much longer 
than in P. nigra. Capsules larger than in P. nigra, more loosely arranged, on slender pedicels 
about 6 — 10 mm. long. 
According to Loudon (Arboret. Brit, iii, 1656 (1838)), this “used to be very commonly propagated in 
nurseries and extensively introduced into plantations ; but, within the last thirty years, the black Italian poplar 
[see below] has been substituted for it.” It is now either very rare, even in cultivation, in this country, or 
overlooked. 
Europe (not indigenous); North America, from Florida and western Quebec westwards to the Rocky 
Mountains. 
*P. deltoidea x nigVCL var. geyi'uina comb. nov. ; P. monilifera x nigra Figert in Deutsche Bot. 
Monatschr. v, no (1887); in A tig. Bot. Zeitschr. i, 159 (1895). 
It would appear that the American species P. deltoidea, soon after its introduction into Europe, hybridised with 
the European P. nigra. Several hybrid-forms, the results of the crossing of the two species, are now in cultivation in 
the country ; and, of these, the two following appear to be sufficiently at home in wild-looking localities to deserve a 
place in the present work. 
(A) x *P. serotina comb, nov.; P. monilifera Michaux fil. Hist. Arb. Forest, iii, 295 (1813) non Aiton ; 
P. serotina Hartig V. Naturg. Forstl. Culturpfl. 437 (1851); Dode op. cit. 44 (1905); P. canadensis Ascherson 
und Graebner Syn. iv, 33 (1908) excl. syn. Marshall non Moench. 
P. nigra foliis acuminatis ad marginem undulatis Duhamel Trait l Arbres ii, 178, t. 39, fig. 5 (1755). 
leones : — Camb. Brit. FI. ii (1913). Plate ip. ( a ) Twig with staminate catkins. ( b ) Staminate flower 
(enlarged), (c) Bracts (enlarged). ( d ) Shoot in summer. ( e ) Bases of leaves (enlarged). Huntingdon (E. W. H.). 
Tree, closely resembling P. deltoidea in habit, differing from it in the following characters: — 
Laminae less cordate at the base ; margin glabrous, less cartilaginous, less coarsely hooked, apex 
less abruptly acute. Stamens about 20 — 30. From P. nigra, it differs in the following characters : — 
Branches curved-ascending, regular, as in P. deltoidea. Winter-buds much longer. Laminae of 
some of the leaves of every twig with 1 — 2 glands at or near the junction of the petiole, 
margin more coarsely hooked, less acuminate ; bronze-coloured when unfolding, dark green later ; 
the last poplar to unfold its leaves. Staminate catkins longer and stouter. Stamens more numerous. 
Pistillate plants are unknown. 
Although not indigenous, this is by far the commonest poplar in the British Isles.- It is planted in almost every 
conceivable kind of situation, including hedgerows, plantations, and the borders of woods, northwards to Caithness- 
shire. Being always a staminate tree, it is reproduced by cuttings. There are, however, in the nurseries, some 
closely allied forms which are pistillate: these occur rarely in cultivation, and will no doubt become commoner 
as time goes on : they have mostly been supplied with binominals by Dode (op. cit.), and reduced to races or 
varieties or subvarieties or forms by Ascherson urtd Graebner (op. cit.). The tree is probably a product of 
the nurseries, where it is known as the black Italian poplar, or in France and Belgium le peuplier Suisse. 
Europe ; North America. 
(B) x *P. canadensis comb, nov.; P. canadensis Moench Bdurne Weissenst. 81 (1785); Hartig V. Naturg. 
Forstl. Culturpfl. 436 (1851); P. euxylon Dode op. cit. p. 41 (1905); P. canadensis var. euxylon Ascherson und 
Graebner Syn. iv, 34 (1908). 
leones : — Camb. Brit. FI. ii (1913). Plate 16. (a) Twig with pistillate catkins, (b) Pistillate flowers (en- 
larged). (c) Shoots in early summer, (d) Base of leaf (enlarged). Planted tree, Cambridge (C. E. M.). 
Tree, nearly as tall as P. deltoidea and x P. serotina. Branches more spreading. Young 
twigs glabrous. Winter-buds long and pointed. Petioles glabrous, shorter than the laminae. Laminae 
ovate-acuminate, cuneate at the base, crenate, glabrous. Pistillate catkins pendulous, very lax, 
10 to 12 cm. long, April. Stigmas yellowish-green. Capsules subspherical. Pedicels 2 — 3 mm. long. 
Staminate trees are unknown. 
Naturalised in fenny places, by streams and rivers, where it is sometimes associated with x P. serotina and 
P. nigra, as in Suffolk. Also planted in gardens and avenues. Probably of garden origin, like x P. serotina. 
Europe. 
P. deltoidea x nigra var. betulifolia (see page 11). 
Section III. *T AC AM AH ACC A. 
*Tacamahacca Spach in Ann. Sci. Nat. xv, 32 (1841); Ascherson und Graebner Syn. iv, 15 et 46(1908). 
For characters, see page 5. Only British species : — *P. tacamahacca. 
