258 NATURAL HISTORY OF PLANTS. 



GynsDcium, ovules, &c., of Betula. Fruit dry, compressed, wingless, 

 or surrounded by a membranous wing, indebisoent ; seed generally 

 1 (of Betula). — Trees or sbrubs ; leaves alternate ; vernal floration 

 preceding or simultaneous (Phyllothyrsus^ Clethropsis) witb leaves ; 

 scales of male catkins peltate, 5-bracteolate, 1- or oftener 3-florous ; 

 scales of female catkins cuneiform, shortly (from adnate bracteoles) 

 4-5-lobed, incrassate above, at maturity separating from eacb other, 

 not deciduous, lignescent ; cones short. (Temp, and frigid regions 

 of both worlds, temp. South America^ South Africa.) — See p. 223. 



II. CORYLE^. 



3. Corylus T. — Flowers amentaceous monoecious ; males naked ; 

 stamens 4-8 (very rarely 2, 3), inserted within scales of catkin ; 

 filaments short free ; anthers 1-locular (or 2-locular; cells separate), 

 extrorsely rimose. Female flowers 2-nate budlike in axils of bracts 

 of catkins ; receptacle saclike, enclosing inferior adnate germen, with 

 very short annular epigynous calyx ; style branches 2, linear 

 elongate, densely stigmatose papillose. Ovules in cells 2 solitary 

 (or more rarely 2-nate) descending ; micropyle extrorsely superior. 

 Nuts more or less ligneous, 1-locular ; walls very thick meduUose 

 below. Seed generally by abortion 1 ; cotyledons of thick exalbu- 

 minous embryo fleshy plano-convex, epigeous at germination ; 

 radicle short superior and united to base of cotyledons. — Small trees 

 or shrubs ; leaves alternate dentate or penninerved, in vernation 

 longitudinally plicate as to the central nerve, and hence on one side 

 facing axis ; stipules caducous ; catkins precocious ; bracts of males 

 cuneiform, generally covering 2 bracteoles, connate within (some- 

 times 0) ; female catkins short subsessile, finally stipitate to elongate 

 foliate ramule ; each fruit surrounded by a sacciform accrescent 

 bracteole at sometimes open tubular apex dentate, laciniate or 

 spinescent, very rarely (Ostryopsis) with external accrescent scale, 

 divided within. {Northern temperate regions of both hemispheres). 

 ^See p. 225. 



4. Carpinus T. — Flowers nearly of Corylus; the males consisting 

 of stamens go (3-20) inserted in axil of bracts of catkin ; filaments 

 slender 2-fid; anther cells separate, pilose at apex and extrorsely 



