28 CONTRIBUTIONS FROM THE NATIONAL HERBARIUM. 
the branchlets bearing 1 to 3 short-pediceled spikelets, the setiform prolongation of the 
axis usually about as long as the spikelets, sometimes twice as long; spikelets 3 to 3.2 
mm. long, 1.7 to 1.8 mm. wide, obo- 
vate, subacute, turgid, strongly nerved; 
first glume clasping, half the length 
of the spikelet, pointed, 5 to 7- 
nerved; second glume and _ sterile 
lemma subequal, scarcely covering the 
fruit, 5 to 7-nerved, the glume ob- 
scurely reticulated toward the summit; 
fruit 2.7 to 2.8 mm. long, 1.6 to1.7 mm. 
wide, obovate-elliptic, abruptly acute, 
very turgid, 
Type U. 8. National Herbarium no. 
592755, collected May 27, 1904, Elsordo, Zapata County, Texas, by David Griffiths 
(no. 6446). 
This species resembles P. ramisetwm, from which it differs in the larger spikelets, 
usually longer sete, broader, more or less ciliate blades, and markedly knotty rootstock. 
Fig. 10.—Distribution of P. firmulum. 
DISTRIBUTION. 
Sandy prairies, southern Texas. 
Texas: Elsordo, Griffiths 6446; Sarita, [Hitchcock 3866; without locality, Nealley. 
TRUE PANICUM. 
SYNOPSIS OF GROUPS. 
Inflorescence consisting of several spike-like racemes along a 
main axis; fruit transversely rugose. 
Perennials; culms spreading or creeping; spikelets gla- 
brous ............. wee eee eee eee eeeee GEMINATA (p. 30). 
Annuals; spikelets pubescent or glabrous................FASCICULATA (p. 35). 
Inflorescence an open or contracted panicle, or if with race- 
mose branches fruit not transversely rugose. 
Annuals; panicles open, usually diffuse. (See also Laxa 
and P. costaricense no. 76.) 
Spikelets glabrous, not warty nor rugulose; fruit pol- 
ished. 
First glume less than one-fourth the length of the 
spikelet, obtuse or truncate; sheaths glab- 
rous except in P. bartowense.............- DICHOTOMIFLORA 
». 47). 
First glume nearly half the length of the spikelet (Pe) 
or more; sheaths hispid (sometimes glab- 
rous in P. decolorans and P. stramineum)..CAPILLARIA (p. 54). 
Spikelets warty, rugulose, or hispid; fruit not polished, 
margins of lemma not inrolled. 
Spikelets 2 mm. or more long; not tropical species. VERRUCOSA (p. 126). 
Spikelets not over 1.4mm. long; tropical species. TRicHorp1a (p. 129). 
Perennials (two species in Laxa annuals). 
Fruit transversely rugose (very faintly so in P. ple- 
num); spikelets ellipsoid, glabrous; plants 
50) 6) 0) ac Maxima (p. 78). 
Fruit not transversely rugose. 
Spikelets densely silky-villous, 6 to 7 mm. long; 
lemma silky on the margins.............. URVILLEANA (p. 132). 
