Quercus L.

3. Quercus L. View in CoL 2

Trees or shrubs. Buds ovoid. Leaves usually dentate, sinuate or pinnately lobed, rarely entire; evergreen (persisting for more than a year), semi-evergreen (persisting green through the winter, but falling in spring), or deciduous (withering in autumn, though sometimes not falling till spring). Flowers anemophilous. Male catkins slender, pendent; bracts minute, caducous; flowers numerous, with usually 6-lobed perianth and 6-12 stamens. Female catkins with few flowers, each solitary in an involucre. Styles 3-6. Fruit an oblong or ellipsoidal nut, its base enclosed by the enlarged involucre (cupule). Germination hypogeal.

In the descriptions and key ‘lateral veins ’ indicates those which run to the apices of the teeth or lobes; in some species intercalary veins, which run to the sinuses or do not reach the margin, may also be present.

In many species leaf-shape is very variable, and the leaves of leading shoots or of young trees may differ considerably from the descriptions given below.

Within each subgenus most species are interfertile. Hybrids are therefore common in regions where related species grow together, and much of the intraspecific variation is due to introgressive hybridization.

Literature: A. Camus, Les Chênes: Monographie du genre Quercus 1-3. Paris, 1936-54. O. Schwarz, Cavanillesia 8: 65- 100 (1936). O. Schwarz, Feddes Repert. (Sonderbeih. D.) 1 -200 (1936-9). J. de Carvalho e Vasconcellos & J. do Amaral Franco, Anais Inst. Sup. Agron. (Lisboa) 21: 1 -135 (1954). C. Vicioso, Revision del Gènero Quercus en Espaha. Madrid, 1950.

1 Leaves evergreen, coriaceous

2 Matureleavesglabrous;veinsprominentabovebut not beneath; petiole 1-4 mm 3. coccifera 2 Matureleavestomentosebeneath; veins± immersedabove, prominent beneath; petiole 5-15 mm

3 Midribof leafsomewhatsinuous;barkverythick,corky

6. suber 3 Midribof leafstraight;barknotthickandcorky

4 Leaves lanceolate to oblong-ovate; stipules thick, hairy;

nut bitter 4. ilex 4 Leaves broadly ovate to suborbicular; stipules membranous, glabrescent; nut sweet 5. rotundifolia 1 Leaves deciduous or semi-evergreen, seldom very coriaceous

5 Fruits ripening in the second year (situated, therefore, on leafless part of twig)

6 Some,at least,of the involucralscalespatentor deflexed

7 Mature leaves glabrous and shining; petiole 2-5 mm

7. trojana 7 Mature leaves pubescent or scabrid, dull; petiole usually more than 10 mm

8 Teeth or lobes ofleaf aristate; upper surface ofleaf smooth

8. macrolepis 8 Teeth or lobes of leaf obtuse or slightly mucronate; upper surface of leaf rough 9. cerris 6 Involucral scales all closely appressed

9 Leaves 10-15 cm wide, lobed not more than half-way to midrib; involucre 18-25 mm wide 1. rubra 9 Leaves 5-10 cm wide, lobed more than half-way to midrib; involucre 10-15 mm wide 2. palustris

5 Fruitsripeningin thefirstyear(situatedamongtheleaves) 10 Scales of fruiting involucre concrescent except for their small triangular apices; fruits usually distant, on a fairly long peduncle 11 Leaves with 8-14 pairs of straight, parallel lateral veins; intercalary veins absent 14. hartwissiana 11 Leaves with 5-9 pairs of often rather irregular lateral veins; intercalary veins usually present 12 Leaves glabrous; lateral veins mostly straight 15. robur 12 Leaves greyish-puberulent beneath; lateral veins arising at an acute angle with the midrib, but then curving outwards towards margin 16. pedunculiflora 10 Scales of fruiting involucre distinct, not concrescent; fruits usually crowded; peduncle short or almost absent 13 Leaves deciduous 14 Young twigs tomentose; petiole not grooved 15 Leaves with usually more than 8 pairs of parallel lateral veins; intercalary veins 0; indumentum brownish 16 Leaves 4-8 cm; petiole 10-20 mm; involucre up to 22 x 25 mm 17. sicula 16 Leaves 10-20 cm; petiole 2-6 mm; involucre not more than 12x 15 mm 18. frainetto 15 Leaves with usually fewer than 8 pairs of lateral veins, which are not strictly parallel, and often mixed with intercalary veins; indumentum white or grey 17 Scales of involucre narrowly lanceolate, obtuse, not appressed 18 Leaves densely white-pubescent beneath 19. pyrenaica 18 Leaves grey-green beneath 20. congesta 17 Scales of involucre ovate-lanceolate, ± acute, appressed 19 Lower scales of involucre broad and glabrescent, upper narrower and pubescent; lateral veins diverging from midrib almost at a right angle 21. brachyphylla 19 Scales of involucre ± uniform; lateral veins diverging from midrib at an acute angle 20 Petiole 15-25 mm; scales of involucre loosely appressed 22. virgiliana 20 Petiole 5-12 mm; scales of involucre closely appressed 23. pubescens 14 Young twigs glabrous, or sericeous; petiole grooved 21 Leaves with c. 10 pairs of lateral veins; intercalary veins absent; fruiting peduncles with appressed hairs 10. mas 21 Leaves with 6-8 pairs of lateral veins; intercalary veins usually present, at least near base of leaf; fruiting peduncles glabrous 22 Scales of involucre puberulent, not tuberculate; mature leaves pubescent beneath, at least in the vein-axils 12. petraea 22 Scales of involucre subglabrous, strongly tuberculate; mature leaves glabrous beneath 23 Leaves somewhat coriaceous, regularly sinuate; involucre brownish 11. polycarpa 23 Leaves thin, deeply and irregularly lobed; involucre greyish 13. dalechampii 13 Leaves semi-evergreen 24 Low shrub, seldom more than 50 cm; leaves subsessile 26. fruticosa 24 Tree or tall shrub; petiole more than 5 mm 25 Young twigs and leaves with abundant, fioccose caducous hairs 24. canariensis 25 Indumentum variable, but not fioccose and caducous 26 Leaves dull above; twigs and leaves usually glabrescent 27. infectoria 26 Leaves somewhat shining above; twigs, and usually lowersideofleaves, with persistentpubescence 25. faginea