432 Ulmace.e. 



ELM FAMILY. ULMACE^. 



Trees and shrubs with tough wood and of about one hundred and forty species grouped 



in thirteen genera and widely distributed throughout the temperate regions of the northern 



hemispliere. Five genera are represented in the United States, and three of these by trees 



■of the eastern and southern states. They are characterized as follows : 



Leaves deciduous, simple, petolate. alternate, in two ranks, serrate, pinnately veined, 

 unequal at base, conduplicate in the bud and with usually fugacious stipules ; buds with 

 several scales. Flowem small, perfect, monoecious or polygamous, clustered, or the pistillate 

 solitary: calyx regular, 4-9-parted or lobed ; petals none; stamens as many as the lobes of the 

 calyx and opposite them, with straight exserted filiments and introrse 2-(elled anthers opening 

 longitudinally : ovary 1-celled with solitary, anatropous or aniphitropous ovule suspended 

 from apex of the cell: styles two. fV«i7 a samera. drupe or nut: seed with little or no 

 albumen, straight or curved embryo, and usually fiat cotyledons. 



KEY TO THE GENERA. 



a Fruit a samara; flowers perfect and usually expanding before the leaves.... Ulmus. 



a- Fruit papillose nut-like; flowers polygamous, expanding with the leaves Planera. 



a^ Fruit o drupe ; flowers on the new growth of the season Celtis. 



THE ELMS. Genus UL^IUS L. 



Trees or rarely shrubs with scaly ridged bark, heavy tough wood and somewhat zigzag 

 branchlets, and of about eighteen species, of which six or seven are found in eastern United 

 States and four of these in the northeastern states. None are found in the Pacific states. 



Leaves inequilateral, straight- veined and simply or doubly serrate: stipules scarious 

 caducous: buds with several closely imbricated scales in 2 ranks. Floirers from axillary 

 buds on twigs of the previous season's growth and usually expanding before the leaves (or in 

 autumn from the axils of the leaves of the season), mostly perfect and in fascicles or 

 racemes, with bibracteolate pedicels ; calyx campanulate, membranaceous persistent with 

 4-0 imbricated lobes; stamens 5-(), exserted with slender filaments and oblong anthers; ovary 

 sessile or stalked, compressed with 2 divergent styles stigmatic on inner faces. 1-celled and 

 containing a single aniphitropous ovule. Fruit a flat orbicular or oblong membranaceous 

 1-seeded samara winged all around (or excepting apex), subtended by the withered calyx 

 and sometimes tipped with the remnants of the styles ; seed compressed with straight embryo 

 and no nlbumen. 



Ihuiis is the ancient Latin name of the Elm. 



KEY TO THE SPECIES. 



a Leaves smooth or nearly so above and samara with wing-like ciliate margin 

 b As broad as seed portion 



Samara with glabrous sides ; buds glabrous and bluntly pointed . . U. Americana. 



Samara hairy on sides; buds acuminate and puberulous U. raceniosa. 



h- Narrower than seed portion; branchlets corky winged; samara narrow, stipitatc and 



hirsute U. alata. 



a- Leaves very rough above: samara not ciliate; buds rusty-tomentose. ... U. pubescens. 

 F'or speeies see pp. 182-180. 



THE PLANER TREE. Genus PLANERA Gmelin. 



A genus of a single species of small trees of southeastern United States and the lower 



Mississippi valley, resembling the Elms. The characters are given in the description of species. 



It is named after .John Jaeoh Planer, a German Prefessor of Botany of the eighteenth 



century. 



For speeies see pp. lOO-lflL 



THE HACKBERRIES. Genus CELTIS L. 



Trees and shrubs of fifty or sixty species, widely distributed throughout the temperate 



and tropical regions. Four species are found in North America, two being shrubs of the 



southern states and southward and the other two trees entitled to consideration here. 



Leaves pointed, inequilateral pinnately-veined or sometimes .3-5-veined at base: stipules 

 membranous, caducous. Flowers polygamo-monoecious, small, appearing with the unfolding 

 of the leaves or soon after on the branchlets of the year, pedicellate : the staminate in 

 fascicles near the base of the shoot and the i)istillate solitary or few together from the axils 



