8 
POP ULUS 
laterally compressed, and leaves therefore very tremulous. Laminae suborbicular or suborbicular- 
acute, coarsely toothed, glabrous at least at maturity, very tremulous ; of the sucker-leaves with 
relatively shorter petioles, grey with hairs, cordate or ovate, more evenly serrate, teeth ending 
with a reddish gland, two reddish glands near the junction of the petiole. Catkins late February 
and early March. Staminate catkins about 5 — 8 cm. long. Bracts deeply laciniate. Stamens about 
12. Pistillate catkins about 4 — 6 cm. long. Bracts deeply laciniate, hairs longer and more numerous 
than in P. canescens. Stigmas purple, suberect, broader than in P. canescens. Pedicel glabrous. 
Capsule narrowly elliptical, acute or subacute. 
(a) P. tremula var. sericea [Lang ex] Doll Rhein. FI. 259 (1843); P. villosa Lang in Syll. Soc. Ratisb. 
i, 185 (1824)!; P. tremula var. villosa Syme Eng. Bot. viii, 196 (1868); Rouy FI. France xii, 250 (1910); P. 
tremida race villosa Ascherson und Graebner Syn. iv, 27 (1908). 
leones : — Reichenbach Icon. t. 617, fig. 1273, as P. canescens , excluding the stigmas which are copied from 
Eng. Bot. t. 1619. 
Camb. Brit. FI. ii (1913). Plate 6 . (a) Normal shoot, with mature leaves, (b) The same, with very young 
leaves, (c) Sucker-shoots and leaves, (d) Shoots with pistillate catkins, (e) Shoot with staminate catkins. 
(/) Pistillate flowers, each with a bract (enlarged), (g) Staminate flower and bract (enlarged). 
Exsiccata : — Reichenbach, 1633, as P. villosa. 
Leaves when unfolding covered with long, silky, appressed hairs, becoming glabrous in summer 
and autumn. Laminae of the sucker-leaves and of the leaves of coppiced shoots up to twice as 
large as those of var. glabra , and cordate. Bracts rather larger and with rather longer hairs 
than var. glabra , and broader laciniations. 
This variety is the commoner form in southern England where it is indigenous on stiff soils in ash woods, 
in ash-oak woods, and in oak woods. We have seen it growing in such habitats in Somerset, Cambridgeshire, 
and Huntingdonshire; and it has been reported to us from Hampshire, Surrey, and Kent. Not recorded for 
Wales, Ireland, or Scotland. Dode (op. cit. p. 30) and Rouy (op. cit. p. 251) agree in regarding it as commoner 
in France than var. glabra. 
Western, central, and southern Europe. 
(b) P. tremula var. glabra Syme Eng. Bot. viii, 196 (1868); P. tremida var. genuina Wesmael in 
DC. Prodr. xvi, pt. ii, 325 (1868); P. tremida Dode op. cit. 30 (1905); P. tremida race typica Ascherson 
und Graebner Syn. iv, 25 (1908); P. tremula var. dodeana Rouy FI. France xii, 250 (1910). 
leones: — Svensk Bot. t. 103, as P. tremula\ Smith Eng. Bot. t. 1909, excluding the bract which should 
be ciliate, as P. tremula ; FI. Dan. t. 2184, as P. tremula ; Reichenbach Icon. t. 618, fig. 1274, as P. tremida. 
Camb. Brit. FI. ii (1913). Plate 7. (a) Winter-twig, (b) Shoot with staminate catkins. ( c ) Leaves. 
(d) Staminate flowers and bracts (six enlarged). Plate 8 . (a) Shoot with mature leaves, (b) Sucker-shoot. 
(c) Portion of leaf (enlarged) of sucker-shoot, (d) Twigs with pistillate catkins, (e) Bract (enlarged). (/) Pistil- 
late flowers and bracts (enlarged), (g) Hermaphrodite flower (enlarged), (h) Leaf-bud (enlarged). Cambridgeshire 
(R. H. A.) and Huntingdonshire (E. W. H.). 
Exsiccata : — Billot, 2742, as P. tremula ; Fellman, 221, as P. tremula ; Hb. FI. Ingric. vi, 576, as P. tremula. 
In the Linnaean herbarium there are two sheets named P. tremula\ one is this species, probably var. glabra ; 
and the other is perhaps the American species P. grandidentata. 
Laminae glabrous or sparsely hairy when very young ; of the sucker-leaves small (about 
3 to 6 cm. long), suborbicular-ovate, not cordate, hairy, regularly toothed. 
In the hilly and rainy districts of western and northern Great Britain and of Ireland, var. glabra is 
the commoner if not indeed the only form of the species : in the south and east of England, this variety 
is rare; Cambridgeshire, Huntingdonshire, Derbyshire, Perthshire, Inverness-shire, Caithness-shire. Dr W. G. Smith 
states (m htt.) that P. tremula (probably var. glabra) is indigenous in Edinburghshire. Syme (op. cit. p. 196) 
reports it from Aberdeenshire. We have also seen specimens from the following counties ; but it is impossible to 
state whether or not the specimens were gathered from indigenous or from planted trees : — Sussex, Suffolk, 
Shropshire, Denbighshire, Kircudbrightshire, Inverness-shire. Ascends to 480 m. on the Pennines. 
It is said to have the same range abroad as the species (Ascherson und Graebner op. cit. p. 26). In the 
warmer districts, it occurs in the more mountainous and rainier parts. 
Damp woods and scrub, streamsides and marshes, throughout the British Isles, but rather local. 
Europe, northern Africa, northern, western, and central Asia. 
The British members of the section Leuce furnish an interesting sequence of forms as regards the hairyness of the 
winter-buds, twigs, and leaves. The degree of hairyness is correlated with the climate of the distributional area of the 
plants. P . alba , the most hairy, is indigenous in the driest and warmest region, P. tremula var. glabra in the wettest and 
coldest. P. canescens and P. tremula var. sericea are intermediate in both respects. 
P. canescens x tremula (page 7). 
