URTICACEJB. 329 



SUBORDER I. ULMLACE^E. (ELM FAMILY.) 



Flowers perfect or mouoeciously polygamous. Filaments straight or 

 moderately incurved in the bud. Styles or stigmas 2. Fruit a samara 

 or drupe. Trees, with alternate leaves. 



1. Ulmus. Flowers sometimes perfect. Ovary 2-ovuled. Fruit a samara. Anthers 



extrorse. 



2. Celtis. Flowers polygamous. Ovary 1-ovuled. Fruit a drupe. Anthers introrse. 



SUBORDER II. URTICE^E. (NETTLE FAMILY.) 



Flowers monoecious or dioecious. Filaments wrinkled and inflexed in 

 the bud. Style or stigma simple. Ovary always l-celled and 1-seeded, 

 becoming an akene. Herbs with a tough fibrous bark and opposite or 

 alternate leaves. 



* Calyx in the fertile flowers of 2 to 5 separate or nearly separate sepals : plant beset with 



stinging bristles. 



3. Urtica. Sepals 4 in both sterile and fertile flowers. Akene straight and erect, enclosed 



by the 2 inner and larger sepals. Stigma capitate-tufted. Leaves opposite. 



4. Laportea. Sepals 5 in the sterile flowers, 4 in the fertile, or apparently only 2, the 



two exterior being minute. Akene very oblique and' bent down, nearly naked. Stigma 

 long and awl-shaped. Leaves alternate. 



* * Calyx of the fertile flowers tubular or cup-shaped, enclosing the akene. Plant wholly 



destitute of stinging bristles. 



5. Parietaria. Flowers polygamous, in involucrate-bracted clusters. Stigma tufted. 



Leaves alternate* 



SUBORDER III. CANlVABINEjE. (HEMP FAMILY.) 



Flowers dioecious ; the sterile racemed or panicled ; the fertile in clus- 

 ters or catkins. Filaments short, not iuflexed in the bud. Fertile calyx 

 of one sepal, embracing the ovary. Stigmas 2, elongated. Ovary 

 l-celled, 1-ovuled, becoming a glandular akene. Herbs with opposite 

 lobed leaves and a fibrous inner bark. 



6. Humulus. Fertile flowers in a short spike forming a membranaceous catkin in fruit. 



Anthers erect. Leaves 3 to 5-lobed. 



1. ULMUS, L. ELM. 



Calyx bell-shaped, 4 to 9-cleft. Stamens 4 to 9, with long slender filaments. 

 Ovary 2-celled. Fruit winged all around. Flowers polygamous, purplish or 

 yellowish, in lateral clusters, preceding the leaves, which are strongly straight- 

 veined, short-petioled, and oblique or unequally somewhat heart-shaped at 

 base. 



1. U. Americana, (L.) Willd. Buds and branchlets glabrous : branches 

 not corky : leaves obovate-oblong or oval, abruptly pointed, sharply and often 

 doubly serrate, soft pubescent beneath or soon glabrous, smooth above or 

 nearly so : flowers on slender drooping peduncles which are jointed above the 

 middle, in close fascicles : fruit glabrous except the margins, its sharp points 



