534 TREES OF NORTH AMERICA 



mens much exserted ; leaves twice pinnate; cotyledons oval or orbicular, flat; radicle 

 straight. 



Stamens numerous (more than 10) ; seeds without albumen. 

 Filaments more or less united into a tube. 

 Filaments united. 



Valves of the pods not separating at maturity from the margins. 1. Zygia. 

 Valves of the pods separating at maturity from the persistent margins. 



2. Lysiloma. 



Filaments free or the inner ones slightly united at the base. 3. Acacia. 



Stamens 10 ; filaments free ; seeds with albumen. 



Legume piano-compressed, dehiscent ; flowers in globose heads. 4. Leucaeiia. 



Legume terete or compressed, indehiscent ; flowers in cylindrical spikes. 



5. Prosopis. 



Subfamily 2. C.ESALPINIOID.S:. Calyx 5-lobed or toothed, the divisions usually valvate in 

 the bud ; corolla imperfectly papilionaceous or nearly regular ; petals 5, imbricated in 

 the bud, the upper one inside and inclosed by the others ; stamens 10 or less ; filaments 

 free ; anthers introrse ; ovules numerous (sometimes 2 in one species of Gleditsia), super- 

 posed, anatropous, the micropyle superior ; seeds albuminous. 



Flowers imperfectly papilionaceous ; calyx 5-toothed ; legume flat, wing-margined ; 

 leaves simple. 6. Cercis. 



Flowers regular. 



Flowers polygamous or dioecious. 



Calyx-tube elongated, 5-lobed ; petals 5 ; stamens 10, shorter than the petals ; 



legume thick and woody ; leaves twice pinnate. 7. Gymnocladus. 



Calyx-tube short, 3-5-lobed ; petals 3-5 ; stamens 3-5, longer than the petals ; 



legume leathery ; leaves once and twice pinnate. 8. Gleditsia. 



Flowers perfect. 



Legumes linear, torulose, acuminate at the ends, the valves contracted between 

 the seeds ; rachis of the leaf spinescent. . 9. Parkinsonia. 



Legumes oblong-compressed, rachis of the leaf not spinescent. 10. Cercidium. 

 Subfamily 3. PAPILIONAT^E. Calyx of 5 more or less united sepals ; corolla of 5 irregular 

 petals, papilionaceous, the upper petal (standard) larger than the others and inclosing 

 them in the bud, usually turned backward or spreading, the 2 lateral petals (wings) 

 oblong, exterior to the 2 lower connivent more or less united petals (keel) inclosing the 

 stamens and pistil ; stamens 10, 9 of them united into a tube cleft on the upper side, the 

 10th and upper one separate, or all distinct; ovary 1 or many-celled by cross parti- 

 tions ; ovules amphitropous, the micropyle superior ; seeds usually without albumen ; 

 leaves once pinnate. 

 Stamens distinct. 



Flowers in racemes ; legume terete, contracted between the seeds. 11. Sophora. 

 Flowers in panicles ; legume compressed. 12. Cladrastis. 



Stamens diadelphous (9 and 1). 

 Flowers in racemes. 

 Leaves glandular-dotted. 



Leaves many-foliolate ; petals free and distinct. 13. Eysenhardtia. 



Leaves simple ; wings and keel-petals adnate to the tube of the stamens. 



14. Dalea. 

 Leaves without glandular dots. 



Legume compressed ; stipules becoming spinescent, persistent. 15. Robinia. 

 Legume turgid, the valves unequally convex by the growth of the seeds ; 

 stipules 0. 16. Olneya. 



Flowers in axillary panicles ; pod linear, longitudinally 4-winged. 



17. Icthyomethia. 



