MAST-BEARING FAMILY 



445 



whilst in many countries acorns and beech-mast are of great value 

 as food for pigs. 



Tribe i. Betule.'E. — All ftowers in catkins ; ovary of 2 i-ovuled 

 chambers ; fruit small, compressed. 



1. Betula. — Stamens 2; scales of fruit-hearing catkin thin, 

 deciduous. 



2. Alnus. — Stamens 4 ; scales of fruit-bearing catkin woody, 

 persistent. 



Tribe 2. Corvle.e, — Staminate floivers in catkins; anthers tufted 

 with hairs ; carpellate flowers in pairs in axils of leafy bracts ; ovary 

 2-chambered; ovules 2. 



B^TULA PEXDLLA {irilitC Bircll). 



3. Carpinus. — Fruiting spike with numerous leafy scales. 



4. CoRYLUS. — Fruiting spike with a few brown scales. 



Tribe 3. Quercine^e. — Staminate flowers in catkins; carpellate 

 flowers I — 3 together in an involucre of numerous bracts, which 

 enlarges in fruit ; ovary 3 — 6-chambered ; ovules 2 in each 

 chamber. 



5. QuERCUS. — Staminate flowers in a slender interrupted catkin ; 

 stigmas 3. 



*6. Castanea. — Staminate flowers in a long slender catkin; 

 stigmas 6. 



7. Fagus. — Staminate flowers in a globose catkin ; stigmas 3. 



I. Betula (Birch). — Trees and shrubs; flowers all in catkins 

 with 3-lobed, deciduous scales ; stamens 2, with forked filaments ; 



