﻿356 The New York State College of Forest rij 



l-seeded nut. ^\TJiged in some genera; seed small, exalbuminoiis ; cotyledons 

 fleshy, 



KEY TO THE GENERA page 



1. Staminate flowers solitary in the axils of ament-scales; scales of the pistillate 



ament deciduous; nutlet wingless 2 



1. Staminate flowers 3-6 in the axils of ament-scales; scales of the pistillate 



ament persistent, forming a strobile; nutlet winged Betula 3")7 



2. Involucre of the fruit f oliaceous, 3-clef t ; staminate aments enclosed in buds 



during the winter Carpinus 353 



2. Involucre of the fruit saccate, enclosing the nutlet; staminate aments 



exposed during the winter Ostrya 356 



THE HOP-HORNBEAMS. Genus OSTRYA (Michx.) Scop. 



A genus of wide distribution throughout the northern hemi- 

 sphere and including trees with alternate simple leaves, slender 

 terete branchlets, scaly bark, and heavy close-grained wood. 

 Four species have been described, two of which are indigenous 

 to North America. Ostrya virginiana (Mill.) K. Koch., the Hop- 

 hombeam, is widely distributed in the United States east of the 

 Rocky Mountains. The other species is confined to a restricted 

 area in the southwest. 



Leaves alternate, simple, oblong-lanceolate to oval or obovate, acute or 

 rounded at the apex, rounded at the base, short-petioled Flowers monoe- 

 cious, expanding before the leaves; staminate flowers in short-stalked or ses- 

 sile, clustered aments which are preformed the preceding season near the tips 

 of the branchlets, consisting of 3-4 stamens with short, bifurcated filaments 

 terminating in haiiy anthers, inserted on a receptacle at the base of a broadly 

 ovate, acute, concave scale; pistillate flowers in erect, lax aments terminat- 

 ing short leafy branchlets, borne at the base of a narrowly ovate, foliaceous, 

 ciliate scale which persists untU mid-summer, each flower enclosed in a saccate 

 involucre formed from the union of a bract and two bracteoloes; calyx adnate 

 to the ovary; style short, bearing 2 filiform stigmas. Fruit a small, ovoid, 

 compressed, acute nutlet enclosed in an enlarged, pale straw-eolored, saccate 

 involucre, the cluster resembling the fruit of the hop, hence the name 

 Hop-hornbeam. 



THE HORNBEAMS. Genus CARPINUS (Tourn.) L. 

 Carpinus includes about twelve species of small trees or shrubs 

 scattered over the north temperate zone from Quebec to C<. tral 

 America in the New World and through Europe, Asia, China . iid 

 Japan in the Old World. They are characterized by smooth gra/ 

 bark, furrowed and fluted trunks, and a prominently ribbed nutlet 

 subtended by a trilobed, foliaceous, involucral bract. But one 

 species, Carpinus caroliniana Walt, is found in the United States. 



