324 CONTRIBUTIONS FROM THE NATIONAL HERBARIUM. 



Leaves glandular-atomiferous and slightly hairy on the veins beneath, not at 



all tomentose 3. S. schaffneri» 



Leaves tomentose and villous beneath. 



Leaf blades abruptly contracted at the base, scarcely decurrent. 



1. S. pachydisca. 

 Leaf blades cuneate at the base and decurrent on the winged petioles. 



2. S. dumosa. 



1. Sericotheca pachydisca Rydb. N. Amer. Fl. 22: 263. 1908. 

 Known only from the type locality, Tacubaya, Valley of Mexico. 



Shrub with brown branches ; leaves 2 to 3 cm. long, short-petiolate, with few- 

 coarse teeth ; panicles 10 to 15 cm, long. 



2. Sericotheca dumosa (Nutt.) Rydb. N. Amer. PI. 22: 263. 1908. 

 Spiraea dumosa Nutt.; Hook. Lond. Journ. Bot. 6: 217. 1847. 

 Holodiscus dumosus Heller, Cat. N. Amer. PI. 4. 1898. 



Chihuahua and Baja California. Northward to Wyoming; type from the 

 Platte River. 



Shrub, 1 to 2 meters high, often forming large clumps ; leaves 2 to 5 cm. long, 

 obtuse or acute ; panicles 5 to 20 cm. long, very showy. 



The fruit of this and other species is said to have been eaten by the Coahuilla 

 Indians of California and the Tewa of New Mexico. 



3. Sericotheca schaffneri Rydb. N. Amer. PI. 22: 264. 1908. 

 Northern Mexico; type from San Luis Potosl. Arizona. 



Low shrub ; leaves 1 to 3 cm. long, ovate or rounded-oval, obtuse ; panicles 

 5 to 7 cm. long. 



4. Sericotheca fissa (Lindl.) Rydb. N. Amer. Fl. 22: 265. 1908. 

 Spiraea fissa Lindl. Bot. Reg. 26: Misc. 73. 1840. 



Spiraea argentea Benth. PI. Hartw. 82. 1841. Not S. argentea L. f. 1781 

 ? Holodiscus loeseneri Dammer, Repert. Sp. Nov. Fedde 15: 385. 1919. 

 Michoacan to Oaxaca and Veracruz. Guatemala to Costa Rica. 

 Shrub, 2.5 to 3.5 meters high ; leaves 2 to 5 cm. long, acute ; panicles 5 to 15 



cm. long. 



On the Pico de Orizaba the species ascends to 3.300 meters. 



5. Sericothea velutina Rydb. N. Amer. Fl. 22: 265. 1908. 



Southern Mexico ; type from Sierra de San Felipe, Oaxaca. Guatemala. 

 Shrub, 1 meter high or more; leaves 1.5 to 3 cm. long; panicles 5 to 10 cm. 

 long. 



DOUBTFUL SPECIES. 



Spiraea mexicana Schiede; Regel, Ind, Sem. Hort. Petrop. 1857: 58. 1858. 

 Described from cultivated plants of Mexican origin, 



5. ACAENA Mutis ; L. Mant. PI. 145. 1775. 



Low shrubs, or often herbaceous almost throughout; leaves pinnate, stipu- 

 late ; flowers small, spicate or racemose, the calyx covered with barbed prickles ; 

 petals none; stamens 3 to 5 ; fruit a solitary achene. 

 Upper leaflets 1.5 to 2 cm. long, the lower gradually reduced. 



1. A. agrim.onioides. 

 Upper leaflets 0.8 to 1.5 cm. long, the lower scarcely reduced__2. A. elongata. 

 1. Acaena agrimonioides H. B. K. Nov. Gen. & Sp. 6: 231. 1823. 



Known only from the type locality, near Tianguillo. 



Stems purplish ; leaflets 9 to 13, sessile, acute, coarsely serrate. 



I 



