308 TREES OF NORTH AMERICA 



rocky banks of streams; probably of its largest size on the lower Wabash River and its 

 tributaries in southern Indiana and Illinois; on the Edwards Plateau (Kemble, Kerr, 

 Uvalde, Bandera and Real Counties), Texas, a form occurs with nuts sometimes lj' long 

 with deeper cups up to 1' in diameter (var. Brayi Sarg.). 



Section 2. Flowers unisexual (usually perfect in Ulmus); calyx regular; 

 stamens as many as its lobes and opposite them; ovary superior, 1-celled 

 (rarely 2-celled in Ulmus}\ seed 1. 



XI. ULMACE^E. 



Trees, with watery juice, scaly buds, terete branchlets prolonged by an upper lateral 

 bud, and alternate simple serrate pinnately veined deciduous stalked 2-ranked leaves un- 

 equal and often oblique at base, conduplicate in the bud, their stipules usually fugaceous. 

 Flowers perfect or monceciously polygamous, clustered, or the pistillate sometimes soli- 

 tary; calyx 4-9-parted or lobed; stamens 4-6; filaments straight; anthers introrse, 2-celled, 

 opening longitudinally; ovary usually 1-celled; ovule solitary, suspended from the apex 

 of the cell, anatropous or amphitropous; styles 2. Fruit a samara, nut, or drupe; albu- 

 men little or none; embryo straight or curved; cotyledons usually flat or conduplicate. 

 Five of the thirteen genera of the Elm family occur in North America. Of these four are 

 represented by trees. 



CONSPECTUS OF THE NORTH AMERICAN ARBORESCENT GENERA. 



Fruit a dry samara, or nut-like. 



Flowers perfect; fruit a samara. 1. Ulmus. 



Flowers polygamo-moncecious ; fruit nut-like, tuberculate. 2. Planera. 

 Fruit drupaceous. 



Pistillate flowers usually solitary. 3. Celtis. 



Pistillate flowers in dichotomous cymes. 4. Trema. 



1. ULMUS L. Elm. 



Trees, or rarely shrubs, with deeply furrowed bark, branchlets often furnished with 

 corky wings, and buds with numerous ovate rounded chestnut-brown scales closely 

 imbricated in two ranks, increasing in size from without inward, the inner accrescent, 

 replacing the stipules of the first leaves, deciduous, marking the base of the branchlet 

 with persistent ring-like scars. Leaves simply or doubly serrate; stipules linear, lan- 

 ceolate to obovate, entire, free or connate at base, scarious, inclosing the leaf in the bud, 

 caducous. Flowers from axillary buds near the ends of the branches similar to but larger 

 than the leaf -buds, the outer scales sterile, the inner bearing flowers and rarely leaves. 

 Flowers perfect, jointed on slender bibracteolate pedicels from the axils of linear acute 

 scarious bracts, in pedunculate or subsessile fascicles or cymes sometimes becoming race- 

 mose, appearing in early spring before the leaves in the axils of those of the previous year, 

 or autumnal in the axils of leaves of the year; calyx campanula te, o-9-lobed, membranaceous, 

 marcescent; stamens 5 or 6 inserted under the ovary; filaments filiform or slightly flat- 

 tened, erect in the bud, becoming exserted; anthers oblong, emarginate, and subcordate; 

 ovary sessile or stipitate, compressed, crowned by a simple deeply 2-lobed style, the 

 spreading lobes papillo-stigmatic on the inner face, usually 1-celled by abortion, rarely 

 2-celled; ovule amphitropous; micropyle extrorse, superior. Fruit an ovoid or oblong, often 

 oblique, sessile or stipitate samara surrounded at base by the remnants of the calyx, the 

 seminal cavity compressed, slightly thickened on the margin, chartaceous, produced into 

 a thin reticulate-venulose membranaceous light brown broad or rarely narrow wing naked 

 or ciliate on the margin, tipped with the remnants of the persistent style, or more or 



