266 CONTRIBUTIONS FROM THE NATIONAL HERBARIUM. 
Spikelets solitary in each involucre. 
Involucral bristles plumose ....................-.---. 6. P. setosum. 
Involucral bristles not plumose. 
Spikes 10 to 20 cm. long, the axis 1 to 3 mm. thick; 
one bristle longer and stouter than the others. 
Shorter bristles few, scarcely exceeding the 
spikelets; spike stiff, the spikelets closely 
imbricated ............-................ 3. P. crinitum. 
Shorter bristles numerous, about twice as long 
as the spikelet; spike more lax and loosely 
flowered .............-2.-2-.2..0........ 5. P. mexicanum. 
Spikes shorter, mostly less than 10 cm. long, 
rather lax, the axes slender, less than 1 mm. 
thick, 
Spikes few to several; blades rarely over 1 cm. 
Wide.........2.2. 02022 e eee eee ee eee 4. P. pringlet. 
Spikes numerous; blades 3 to 5 cm. wide. 
Bristles few, about as long as the spikelet, 
one elongated ................... -. 1. P. tristachyum. 
Bristles numerous, all exceeding th 
spikelet ......2..2--2.2.-22....2..4. 2. P. bambusiforme. 
1. Pennisetum tristachyum (H. B. K.) Spreng. Syst. Veg. 1: 302, 1825. 
Gymnothriz tristachya H. B. K. Nov. Gen. & Sp, 1: 113. 1816. 
Type locality, ‘‘prope Puembo, in humidis regni Quitensis.”’ 
Rane@e: Southern Mexico to South America. 
HERBARIUM SPECIMENS FROM MExIco: 
Veracruz: Zacuapan, open damp forests, Purpus 2894. Mirador, Liebmann 339. 
Orizaba, Botteri 96, 631, 1209, 1214; Seaton 291; Bourgeau 2543; Miiller 2066. 
Cérdoba, valley, Bourgeau 1664. 
Oaxaca: Cuicatl4n, canyon, Pringle 5559. 
2. Pennisetum bambusiforme (Fourn.) Hemsl. Ind. Kew. 2: 458. 1894.1 
Gymnothriz bambusiformis Fourn, Mex. Pl. 2: 48. 1886. 
Type locality, ‘‘in virgultis argillosis prope Mirador,’’ the type specimen collected 
by Schaffner (no. 338). 
RancGE: Mexico to Paraguay. 
HERBARIUM SPECIMENS FROM MEXICO: 
Micuoacdn: Sierra Madre, Langlassé 849. 
Veracruz: Mirador, Liebmann 338. Orizaba, Botteri 1214. Barranca of Metlac, 
rocky slopes, Pringle 6075. 
Oaxaca: Pluma, Nelson 2884. Oaxaca, Galeotti 5871. 
3. Pennisetum crinitum (H. B: K.) Spreng. Syst. Veg. 1: 302. 1825. 
Gymnothriz crinita H. B. K. Nov. Gen. & Sp. 1: 112. 1816. 
Type locality, ‘in littore lacus Cuiseo, prope La Puerta de Andaracuas, et juxta S. 
Rosa, inter segetes, in regno Mexicano.”’ 
Rance: Southern Mexico. 
HERBARIUM SPECIMENS: 
Jauisco: Rio Blanco, Palmer 514 in 1886. 
GuanasuaTo: Ac4mbaro, along railway, Hitchcock 6936. Irapuato, moist sandy- 
clay plain, Hitchcock 7397. 
1 The combination is here credited to Hemsl. Biol. Centr. Amer. Bot. 3: 507. 1885, 
but the name is there a nomen nudum, being based on an unpublished name and 
without description. 
