370 RUTACEiE. 



1. THAMNOSMA. Flowers 4-merous but pistil dimerous. Calyx 4-lobed, short, persistent. 

 Petals iiiibriLaie in the hud, erect or barely spreading in anthesis, ovate or oblong, in- 

 serted on the base of a thickened creuate or lobed hypogyuous disk, deciduous. Stamens 8, 

 with slender filaments and oval glandular-apiculatc anthers. Uvary 2-lobed, more or less 

 stipitate, with few or several ovules in each cell on a central placenta ; style filiform, entire ; 

 stigma ca])itate. Capsule coriaceous, obcordate or didymous, few-.'*ee(h'd, loculicitlal above ; 

 seeds reniform, witii coriaceous testa and arcuate or incurved embryo in thin albumen. 

 Leaves simple. 



Tribe II. XANTIIOXYLE.E. SliniKs or trees, with aromatic or pungent and 

 bitter bark and foliage, and either unisexual or hermaphrodite flowers. Ovules 

 only a pair in each carpel or cell. Seeds usually solitary ; embryo with superior 

 radicle, mostly fiat cotyledons, and surrounded by some albumen. 



* Carpels or capsule dehiscent : flowers hermaphrodite, 5-merous (sometimes 4-merous) and 

 diplostemonous, symmetrical. 



2. CHOISYA. Sepals imbricate in the bud, deciduous. Petals sjjreading, o])long with 

 narrow base, sliglitly imbricate in the bud, dcciducms. Stamens 10 or 8, with lanceolate 

 filaments, those opposite tlie petals shorter ; anthers somewhat didymous. Hypogynous 

 disk inconspicuous. Ovary 5-lobed to below the middle, pubescent; the carpels conically 

 produced at ajjcx, bearing a pair of subcollateral ovules aliout tlie middle ; styles ventral, 

 filiform-clavate, conuiveut and cohering above, as also the enlarged terminal stigmas. 

 Fruit dry, 4-r)-coccous or by abortion 2-3-coccous ; the mature carpels dorsally corniform- 

 umbonate near summit, at length 2-valved, and the cartilaginous endocarp separating from 

 the thin exocarp ; seeds solitary or sometimes geminate, reniform, with nearly smooth 

 subcrustaceous testa and arcuate embryo in thin albumen (in C. dumosa). Leaves opposite, 

 palmately compound. 



* * Fruit samaroid, indehiscent : flowers hermaphrodite or polygamous, 3-5-merous, usu- 

 ally 4-merous, isostemouous. 



3. HELIETTA. Flowers nearly of Ptelea, but hermaphrodite and carpels as many as 

 petals, united at the axis, separating in fruit into akeniform cocci, each bearing a large 

 dorsal ascending wing. 



4. PTELEA. Flowers monoeciously or dioeciously polygamous. Sepals 4 or 5, small, decid- 

 uous. Petals 4 or 5, commonly 4, much surpassing the calyx, imbricated in the bud, decid- 

 uous. Stamens 4 or .5, with narrow filaments, in sterile flowers inserted at base of a small 

 annular disk; in fertile flowers small and often abortive. Ovary in sterile flowers rudi- 

 mentary ; in the fertile compressed, 2-celled (rarely 3-celled), with a pair of ascending 

 hemitropous ovules in each cell, the lower ovule infertile ; style short ; stigma 2-lobed. 

 Fruit an orbiculate 1-2-celled, 1-2-seeded samara, completely winged all round (the wing 

 thin and reticulated), or in an anomalous species nucumentaceous and almost or wholly 

 wingless. Leaves alternate, palmately trifoliolate. 



* * * Carpels dehiscent : flowers dioecious, 3-5-merous, isostemouous, small. 



5. XANTHOXYLUM. Calyx 3-5-lobed or -parted and petals (mostly imbricated in the 

 bud) as many, in one species either calyx or corolla wanting. Stamens alternate with the 

 petals. Pistil a mere rudiment in the cf flowers ; in ? flowers as many carpels as petals 

 and opposite them, or fewer, or rarely reduced to one, usually on an ovoid disk or short 

 gynopliore, connivent or slightly cohering ventrally (cither as to ovaries or ui)per part of 

 the styles), separating in age. Fruit drnpaccous-follicular, at length partly 2-valved, the 

 endocarp hardly at all separable ; seed solitary or sometimes a pair, ovoid or globular, 

 sometimes with a .^lightly fleshy at length friable outer coat, which falls away from the dark 

 and shining crustaceous inner one ; embryo straight or nearly so in fleshy albumen, with 

 broad and flat cotyledons. Leaves alternate, mostly pinnate. 



* * # * Carpel solitary with almost basal style, in fruit subdrupaceous : flowers her- 

 maphrodite, 4-merous, diplostemonous. 



6. CNEORIDIUM. Sepals 4, persistent. Petals 4, much larger, ovate, much imbricated 

 in the bud. Stamens 8, short, those opposite the petals shorter ; anthers ovate, mucronulate. 



