136 CONTRIBUTIONS FROM THE NATIONAL HERBARIUM. 



Rachis of leaves puberulent to densely hirsute (at least when young). 



Rachis densely hirsute. Leaflets 7-9, oblong-lanceolate or oblanceolate, acuminate ; 

 fruit globose or oblong, 3.5-7 cm. long, the husk thick, the nut angled, pointed, 



thick-shelled, sweet; bud scales numerous, imbricate 2. H. alba. 



Rachis pubescent or puberulent (when young). 

 Bud scales few, valvate; leaflets 7-9, lanceolate or oblong-lanceolate, acuminate, 

 pulverulent when young; fruit nearly globose, 2.5-3.5 cm. in diameter, the 

 husk thin, the nut angled, thin-shelled, 2-2.5 cm. long, very bitter. 



1. H. cordiformis. 

 Bud scales numerous, imbricate; leaflets oblong, oblong-lanceolate, or obovate; 

 fruit globose or nearly so, 3.5-6 cm. in diameter, the husk thick, the nut 

 thin-shelled, sweet. Rachis and twigs puberulent, becoming glabrous. 



5. H. ovata. 



1. Hicoria cordiformis (Wang.) Britton. • Bitternut. 

 Moist woods and low places. May; fr. Sept. Eastern U. S. (Carya amara Nutt. ; 



H. minima Britton.) 



2. Hicoria alba (L.) Britton. Mockernut. 

 Dry deciduous woods. May; fr. Aug.-Sept. Eastern U. S. {Carya tomentosa 



Nutt.; C. albaK. Koch.) 



3. Hicoria glabra (Mill.) Britton. Pignut hickory. 

 Deciduous woods. May; fr. Aug. Eastern U. S. (Carya porcina Nutt.; C. glabra 



Spach.) 



4. Hicoria microcarpa (Nutt.) Britton. Small-fruited hickory. 

 Deciduous woods. May; fr. Oct. Northern states, south to Ga. (Carya micro- 

 carpa Nutt.) 



6. Hicoria ovata (Mill.) Britton. Shag-bark or shell-bark hickory. 



Deciduous woods; Potomac valley. May; fr. Oct.-Nov. Eastern U. S. (Carya 

 alba Nutt.; C. ovata K. Koch.) 



37. BETUIACEAE. Birch Family. 



Seeds winged, small; staminate flowers 3 or more in the axil of each bract; fruit ovoid 

 or oblong, 1.5 cm. long or smaller. 

 Plants shrulis (rarely trees); leaves obovate or oval, obtuse, serrulate. Fruiting 



catkins persistent 4. ALNUS. 



Plants trees, mostly with peeling bark; leaves of an ovate or ovate-oblong type. 



5. BETULA. 

 Seeds not winged; staminate flowers solitary in the axil of each bract; fruit various. 

 Plants shrubs; twigs warty, sparingly glandular-pubescent; leaves broadly cordate- 

 ovate, doubly serrate, 10 cm. long or less. Pistillate flowers clustered; fruit 

 a nut inclosed in a laciniate involucre composed of two bracts. .3. CORYLUS. 

 Plants trees; twigs smooth, sparingly warty, or pubescent; leaves ovate-oblong, 

 cordate or rounded at the base, taper-pointed. 

 Fruiting axis 5 cm. long or more; fruiting bracts foliaceous, 3-lobed, the lateral 

 lobes small, the middle one oblong, serrulate, 2.5 cm. long or less. 



1. CARPINUS. 



Fruiting axis 3 cm. long or less; fruiting bracts becoming saclike, bladdery, 



inclosing the nut 2. OSTB.YA. 



1. CARPINUS L. 



1. Carpinus caroliniana Walt. American hornbeam. Blue beech. 



Along streams and in low ground. Apr.; fr. Aug. Eastern N. Amer. 



