8o 
CORYLUS 
Throughout the British Isles, northwards to Orkney; in woods, scrub and hedgerows; most 
abundant on calcareous soils, especially on limestone, rarest on dry sandy and gravelly soils ; 
forming the principal shrubby undergrowth in almost all the oak woods and ash-oak woods on 
clayey and marly soils in southern England, and usually coppiced; ascending to about 600 m. 
in the Highlands. 
Southern Scandinavia (to about 67° N.), Denmark, Germany, France, central Europe, central 
and southern Russia, Spain and Portugal (southwards to 38° 20'), Italy, Sicily, Balkan peninsula; 
Krim, Caucasus, Asia Minor ; northern Africa (not indigenous). 
Family 3. BETULACEAE 
Betulaceae Agardh Aphor. 208 (1825); Bartling Ord. Pl. 99 (1830); Loudon Arboret. iii, 1677 (1838); 
Regel in DC. Prodr. xvi, pt. ii, 161 (1838); Betuleae Prantl in Pfianzenfam. iii, pt. i, 38 (1894); Ascherson und 
Graebner Syn. iv, 369 (1910). 
Trees or shrubs. Leaves deciduous, simple, alternate, stipulate; stipules consisting of bud- 
scales, caducous. Catkins compound. Staminate catkins compound, the branches being cymes with 
3 flowers. Perianth present in the staminate flowers, absent in the pistillate ones. Stamens 2 — 4. 
Filaments entire or branched. Pistillate catkins compound, the branches being cymes with 2 — 3 
flowers. Ovary of 2 carpels. Stigmas 2, filiform, purplish. Ovary with 2 loculi. Ovules pendulous, 
1 in each loculus, only 1 in each ovary maturing, with 1 integument. True fruit an achene, 
hidden among the scales of the ripe catkin, usually winged. Cupule absent. 
2 genera ; north temperate zone, Andes. 
Genera of Betulaceae 
Genus 1. Betula (see below). Stamens 2, each bifurcated and each branch terminating in a 
half-anther. Pistillate catkins falling at the end of the summer with the achenes ; cymes 3-flowered. 
Bracts 3-lobed, herbaceous. 
Genus 2. Alnus (p. 86). Stamens 4, not branched. Pistillate catkins remaining on the tree for 
several months after the achenes have been shed ; cymes 2-flowered. Bracts 5-lobed, lignified. 
Genus 1. Betula 
By the Rev. E. S. MARSHALL, M.A., F.L.S. 
Betula [Tournefort hist. 588, t. 360 (1719)] L. Sp. PI. 982 (1753) et Gen. PL ed. 5, 422 (1754) partim ; 
Miller Abridg. Gard. Diet. ed. 6 (1771); Prantl in Pfianzenfam. iii, pt. i, 43 (1894); Winkler in Pflanzenr. iv, 
pt. 61, 56 (1904). 
Small trees, shrubs, or undershrubs. Catkins cylindrical, flowering immediately after the ap- 
pearing of the young leaves ; cymes with 3 flowers to each bract. Staminate catkins usually 
pendulous. Perianth with 1 — 3 segments, minute. Stamens 2, each split nearly to the base, the 
lateral ones suppressed. Pistillate catkins very slender, much longer than broad. Pei'ianth absent. 
Ovary 2-locular, 1 -seeded. Fruiting catkins with herbaceous scales which are shaped like the 
heraldic fleur-de-lis , not persisting on the plant after the fruits have been shed. 
Linnaeus, in his Gen. PI. ed. 1, 285 (1737), followed Tournefort in keeping Betula and Alnus as distinct genera. 
Later, he united them ; but in this he is not followed by modern botanists. 
About 40 species, in the north temperate and Arctic zones. 
The British species belong to the subgenus Eu- Betula Regel in Mem. Soc. Nat. Mosc. xiii (16) (1861); in DC. 
Prodr. xvi, pt. ii, 162 (1868). 
British series of Betula 
Series i. Albae (p. 81). Small trees or shrubs. Leaves not crowded, acute to acuminate, 
longer than broad. Achene with a more or less conspicuous wing. 
Series ii. Nanae (p. 86). Dwarf undershrubs of Arctic- Alpine distribution. Leaves crowded, 
suborbicular, broader than long. Achene with the wing rudimentary or absent. 
There is a recent account of the Scandinavian forms of Betula , by N. C. Kindberg, in Botaniska Notiser pp. 113 — 132 
(1909). Kindberg recognises 22 species, 6 subspecies, 10 varieties, and 3 formae. There can be no doubt that Betula 
is far more variable in the British Isles, and especially in Scotland, than previous British floras have indicated ; and it 
may well be that one or two of the birches here placed as varieties of B. pubescens will ultimately be found to be 
worthy of specific rank. However, the number of species allowed by Kindberg would be extravagantly large for the 
British Isles. I have very little doubt that several of the plants to which Kindberg has given binominals are hybrids ; 
and others I think ought to be reduced to varieties or formae. 
