380 CONTRIBUTIONS FROM THE NATIONAL HERBARIUM. 



KEY TO THE GENERA. 



Embryo straight; flowers mostly unisexual, sometimes 

 hermaphrodite; shrubs or trees. 

 Staminate perianth tubular to almost spherical; 



stamens included. (Stems unarmed) 1. Nkea (p. 382). 



Staminate perianth campanulate; stamens ex- 

 serted . 

 Fruit fleshy, not glandular. (Stems unarmed). 2. Torrubia (p. 385). 

 Fruit dry and hard, bearing numerous glands 

 along its angles. 

 Flowers hermaphrodite, umbellate; stems 

 unarmed; low shrubs; stigma de- 

 pressed-capitate 3. Pisoniella (p. 385). 



Flowers unisexual, corymbose; climbing 

 or erect tal! shrubs, or trees; stems 

 armed with thorns or unarmed; 



stigma penicillate 4. Pisonia (p. 386). 



Embryo strongly curved; flowers hermaphrodite; plants 

 herbaceous, or sometimes suffrutescent at the 

 base. 

 Perianth inconspicuous, green, persisting scarcely 

 changed in fruit, not differentiated into a dis- 

 tinct upper and lower part. (Leaves alter- 



nate ) 5. Salpianthus (p. 391). 



Perianth corolla-like and Bhowy, enlarged and en- 

 veloping the fruit, more or less evidently 

 differentiated into two parts, the lower of 

 which adheres to and envelops the fruit, the 

 other deciduous from or persistent upon its 

 summit. 

 Perianth not adhering to the wall of the fruit but 

 enlarged and enveloping it at maturity. 

 Leaves opposite; herbs; embryo spherical; 



fruit not adhering to the bracts G. Colignonia (p. 394). 



Leaves alternate; thorny, woody vines; 

 embryo linear-oblong; fruit adnate 



to the bracts and falling with them. 7. r>ouoAiNviLi,EA (p. 394). 

 Perianth evidently differentiated into two 

 parts of different consistency, part per- 

 sisting as a coat of the anthoearp. 

 (Leaves opposite.) 

 Stigma linear; inner cotyledon abortive; 

 lower part of the perianth without 

 mucilaginous glands; anther cells 

 oblong. 

 Wings of the fruit hyaline, completely 

 encircling the fruit; flowers 



usually tetramerous; stamens 4. 8. Tripterocalyx (p. 395). 

 Wings, when present, thicker and 

 opaque, not completely encir- 

 cling the fruit but interrupted 

 above and below; flowers pen- 

 tamerous; stamens 5 or more. . . 9. Abronia (p. 395). 



