POP ULUS 
7 
below when young, more or less glabrescent ; of the summer-leaves white or grey below, sublobed, 
often remaining small ; of young trees and suckers cordate-ovate, irregularly and coarsely toothed 
or sublobed, with two red glands near the junction of the petiole, white or grey below. Catkins late 
February to mid-March. Staminate catkins opening earlier than the pistillate ones, about 5 — 10 cm. 
long. Bracts strongly laciniate, larger than in P. alba and with hairs relatively shorter. Stamens about 1 2. 
Pistillate catkins about 2 - o — 2 ’5 cm. long, darker in colour and thicker than in P. alba ; in some 
years, they appear 3 — 4 weeks later than the staminate catkins. Bracts strongly laciniate. Stigmas 
yellowish, stouter than in P. alba. Capsules relatively shorter than in P. alba. Seeds with hairs 
shorter than in P. alba. 
This species is often treated as a hybrid of P. alba and P. tremula owing, no doubt, to its having been confused 
with hybrids of P. canescens and P. tremula. We ourselves regard P. canescens as a species distinct from P. alba and 
having a very different distribution from either P. alba or P. tremula. P. canescens has greenish-yellow stigmas not very 
unlike those of P. alba , only rather stouter, not pink or purple ones like P. canescens x tremula (= P. canescens of many 
authorities, e.g., Dode and Rouy, but not of Smith). 
Indigenous but thinly scattered on the damper and richer soils of southern and central England, 
and avoiding (as a native tree) the hills of the north and west. Quite rare and perhaps not 
indigenous in the extreme west and south-west of England. It prefers alluvial soils, chiefly by 
stream-sides ; and, in such localities and on the upland edges of fens in eastern England, it 
is not uncommon. Also in ash-oak woods on marl, as in eastern Somerset, and in oak woods 
on clay, as in Kent. Perhaps indigenous in southern Ireland; probably not so in Wales, northern 
England, or Scotland. As a planted tree, it occurs as far north as Inverness. 
Southern Sweden and Denmark (doubtfully indigenous), and western Europe generally ; central 
Europe; southern Europe from Spain to the Balkan peninsula; Caucasus; Asia Minor. 
P. canescens x tyemula comb. nov. ; P. hybrida Bieberstein FI. Taur. Cauc. ii, 422 (1808); P. alba 
x tremula Neilreich in d. Verhandl. Z.-B. Ver. 120(1851); P. steiniana Bornmiiller in Gartenfl. xxxvii, 173, fig. 37 
et 38 (1888); P. canescens Dode op. cit. 26 (1905); Rouy FI. Fra7ice xii, 249 (1910) partim ; non Smith; P. 
alba x tremula forma steiniana Ascherson und Graebner Syn. iv, 30 (1908). 
leones : — FI. Dan. t. 2183, as P. canescens. 
Camb. Brit. FI. ii (1913). Plate 5. (a) Long shoot, in early summer. ( b ) Leaf of sucker-shoot, under 
side, (e) Leaf of sucker-shoot, upper side, (d) Old pistillate catkin, (e) Pistillate flowers (enlarged). (/) Bracts 
(enlarged). Suffolk (C. E. M.). 
Tree, freely suckering. Bark brownish or brownish-grey. Branches rather regular and ascending. 
Twigs smooth. Buds hairy, acute. Petioles nearly as long as the laminae. Perianth glabrous. 
Laminae suborbicular, irregularly toothed, eventually glabrous ; of the sucker-shoots ovate, truncate 
to subcordate at the base, snowy white with hairs underneath. Catkins March and April. Staminate 
catkins about 5 — 6 cm. long. Bracts short, yellowish, rather pectinate, hairs shorter than the teeth. 
Pistillate catkins about 5 — 8 cm. long. Bracts deeply laciniate, often persistent, with a narrow dark- 
brown border, hairs longer than the teeth. Pedicel glabrous. Stigmas pink to purple. Capsules 
relatively shorter than in P. alba. 
Very rare, or perhaps less rare than would appear to be the case owing to its having been confused with P. canescens. 
Cambridgeshire, Suffolk, Dorset (planted), Hertfordshire. 
Europe (excluding northern and Arctic) ; south-western Asia. 
Series ii. Tremulae 
Tremulae nobis; Trepidae Dode op. cit. 19 (1905) as a section; Ascherson und Graebner Syn. iv, 24 
(1908). 
For characters, see page 5. Only British species : — P. tremula. 
3. POPULUS TREMULA. Aspen. Plates 6, 7, 8; 5 
Populus lybica Gerard Herb. 1302 (1597); Ray Syn. ed. 3, 446 (1724). 
PopulllS tremula L. Sp. PI. 1034 (1753); Syme Eng. Bot. viii, 196 (1868); Ascherson und Graebner 
Syn. iv, 24 (1908); Rouy FI. France xii, 250 (1910). 
Tree, growing to a height of about 20 m., suckering freely. Bark dark grey below, paler 
above. Winter-buds glabrous, acute. Stipules setaceous. Petioles usually longer than the laminae, 
