ULMACEAE 107 



KEY TO GENERA 



I. Fruits drupaceous ; flower on the current year's shoots. 



A. Sepals connate; style eccentric; fruit oblique. 



1. Branchlets armed; leaves dotted ■with minute circular 

 black depressions; fruits winged Hemiptelea. 



2. Branchlets unarmed ; leaves without minute dots ; fruit 

 not winged Zelkova. 



B. Sepals distinct or nearly so; style central; fruit globose. 



1. Drupe winged; wing somewhat woody Pteroceltis. 



2. Drupe not winged. 



a. Fertile flowers unisexual; leaves with straight veins 

 ending in the teeth Apananthe. 



b. Fertile flowers perfect; leaves with curved veins 

 closed before reaching the margin. 



(1) Leaves evergreen ; flowers in cymes Trema. 



(2) Leaves deciduous; pistillate flower solitary.. .Celtis. 



II. Fruits not drupaceous, winged; samara membranous; flowers 

 on last season's shoots, (except 1 species) Ulmus. 



ULMUS 



Mostly deciduous trees. Leaves 2 ranked, simple, alternate, serrate, 

 pinnately veined with straight veins, oblique at the base, stalked, stipules 

 2. Flowers small, apetalous, perfect, rarely polygamous, in clusters or 

 fascicles, appearing before the leaves in the spring, or in the axils of the 

 leaves in the autumn; calyx persistent, bell-shaped, greenish or tinged 

 with red, 4-9 lobed; stamens equal to and opposite the calyx lobes, 

 exserted, inserted at the base of the perianth; ovary superior, usually 1 

 celled and 1 ovuled. Style 2-lobed. Fruit a membranous samara, with 

 a flat orbicular or oval wing notched at the apex and surrounded at the 

 base by the persistent calyx. 



About 20 species in N. America, Europe, and Asia. 

 The wood is hard, heavy, and tough, much used in the wood-work- 

 ing industries. The inner bark is an ingredient in the composition of 

 incense; it is also made into a, rn.ucilagir.ous meal, used as food by the 



