Populus L.

2. Populus L. View in CoL 1

Deciduous trees. Buds with several unequal scales. Leaves usually ovate or triangular, entire, dentate or lobed. Petiole usually long, terete or flattened. Flowers anemophilous, appear­ ing before the leaves, in pendent stalked catkins, each flower with a stalked, cup-shaped disc and subtended by a toothed orlaciniate bract. Stamens 4 to many. Capsule 2- to 4-valved. Seeds numerous, minute.

Many hybrids, most of them of recent origin, are now planted for pulp-wood in Europe.

1 Pistillate flowers long-pedicellate, with caducous disc; leaves very variable, some, particularly towards end of longshoots, lanceolate or linear-lanceolate 11. euphratica

1 Pistillate flowers subsessile, with persistent disc; leaves variable butnever lanceolate

2 Leavesof longshootsdenselytomentosebeneath,thoseof short shoots less tomentose or subglabrous

3 Leaves of long shoots palmately lobed, white-tomentose beneath; bracts dentate 1. alba

3 Leaves of long shoots with wide irregularly serrate teeth, grey-tomentose beneath; bracts laciniate 2. canescens

2 Leavesnottomentosebeneath(sometimesthinlytomentose when very young)

4 Leaves without a translucent margin

5 Petioles strongly compressed

6 Leaves cuneate or truncate at base, coarsely dentate; buds grey-tomentose 3. grandidentata 6 Leaves rounded or subcordate at base, sinuately crenate- dentate; buds glabrous, slightly viscid 4. tremula

5 Petioles terete

7 Leaves rhombic-elliptic to obovate, cuneate at base;

petioles 0-5-2-5 cm; twigs glabrous 5. simonii

7 Leaves deltate-ovate, usually cordate; petioles 3-6cm;

twigs hairy 6. gileadensis

4Leaveswitha translucentmargin,sometimes verynarrow 8 Leaves with a very narrow translucent margin; petioles terete, though sometimes grooved on upper side 7. x berolinensis

8 Leaves with an obvious translucent margin; petioles

laterally flattened

9 Leaves 10—18 cm, deltate-ovate to ovate, densely ciliate;

stamens 30-60 10. deltoides

9 Leaves 7-10 cm, rhombic or deflate, ciliate or not;

stamens 15-30

10 Lamina not ciliate, without glands at base; trunk usually with large bosses 8. nigra

10 Lamina shortly ciliate, usually with one or two glands

at base; trunk without bosses 9. x canadensis