STANDLEY TREES AND SHRUBS OF MEXICO. 241 



Similar in general appearance to the last species ; a slender vine with stems 

 2 to 3 meters long ; capsules about 3 cm. long. " Huaco," " zapatito," " palito," 

 " matanene del mar " ( Sinaloa ) . 



In Sinaloa the plant is highly esteemed as a remedy for the bites of snakes 

 and other poisonous animals. 



31. POLYGON ACE AE. Buckwheat Family. 



Shrubs or trees, sometimes scandent ; leaves alternate or rarely opposite or 

 verticillate, entire, stipulate, the stipules often united into a sheath ; flowers 

 mostly small, perfect or unisexual ; corolla none ; fruit a lenticular or 3-angled 

 achene. usually surrounded by the persistent calyx. 



Several other genera, all of whose species are herbaceous, occur in Mexico. 



Plants with tendrils in the inflorescence, scandent 7. ANTIGONON. 



Plants without tendrils. 



Flowers one or more inside an involucre. 



Leaves alternate ; involucre not accrescent in fruit, not colored ; flowers 



perfect 1. ERIOGONUM. 



Leaves opposite ; involucre accrescent in fruit, red or purplish ; flowers uni- 

 sexual 2. HARFORDIA. 



Flowers not involucrate. 

 Flowers normally 5-parted. 

 Perianth lobes not winged. 



Flowers unisexual 3. MUHLENBECKIA. 



Flowers perfect 4. COCCOLOBA. 



Perianth lobes winged. 

 Leaves orbicular ; pedicels not winged ; filaments pubescent. 



5. NEOMILLSPAUGHIA. 

 Leaves not orbicular ; pedicels winged ; filaments glabrous. 



6. PODOPTERUS. 

 Flowers 6-parted or rarely 3-parted. 



Flowers perfect ; perianth segments broadly ovate__8. GYMNOPODIUM. 

 Flowers dioecious ; perianth segments of the fertile flowers long and 

 narrow. 



Stamens numerous ; fruit acutely trigonous 9. TRIPLARIS. 



Stamens 9 ; fruit 3 to 6-sulcate, the angles obtuse. 



10. RUPRECHTIA. 



1. ERIOGONUM Michx. Fl. Bor. Amer. 1:246. 1S03. 



Low shrubs, often toraentose ; flowers surrounded by an involucre, the in- 

 volucres spicate, umbellate, capitate, or cymose, the flowers small but often 

 rather showy. 



Numerous herbaceous species occur in northern Mexico. Most of the species 

 of the genus grow in arid places. 



Leaves not at all tomentose 1. E. orcuttianum. 



Leaves tomentose on one or both surfaces. 

 Perianth densely pubescent. 



Perianth narrowed to a stipelike base ; plants low, Avith depressed stems. 



2. E. undulatum.. 

 Perianth without a stipelike base; plants tall, much branched — 3. E molle. 



