128 THE FLORA OF THE ALPS 



5. CARPINUS, L. 



Fruit I -celled, I -seeded, enclosed in the greatly enlarged 

 leafy lobed involucre. 



C. Betulus, L., Hornbeam ; frequent. 



6. OSTRYA, Scop. 



Female flowers in strobiliform catkins ; fruit I -seeded, 

 enclosed in the bladdery papyraceous involucre. 



O. carpinifolia, Scop. ; leaves oval, acuminate, slightly 

 cordate, doubly serrate ; Grisons, Ticino, rare. 



Order LXXXIL BETULACE^E. 



Flowers unisexual, monoecious; male flowers in pen- 

 dulous catkins, female flowers beneath the scales of the 

 female catkins ; stamens 2-4 ; sepals o in female flowers ; 

 ovary inferior, 2-celled, with one ovule in each cell ; Tem- 

 perate and Arctic Zones. 



i. BETULA, L. 



Stamens 2; scales of female catkin thin, deciduous, 

 3-fid. 



B. alba, L. (verrucosa, Ehrh.), our common Birch. B. 

 pubescens, Ehrh. (glutinosa, Fr.); leaves orbicular or 

 rhomboid, pubescent beneath, fruit with a broad wing ; 

 peat-bogs, local. B. intermedia, Thorn. ; resembling the 

 last, but a shrub ; peat-bogs ; Jura, rare. B. nana } L. ; 

 a small shrub, 1-3 ft., female catkins erect, sessile, 

 leaves broader than long, crenate; peat-bogs at a high 

 elevation ; Switzerland (rare), Jura. 



