42 



CONTRIBUTIONS FROM THE NATIONAL HERBARIUM. 



12. Panicum molle Swartz. 



Panicum molle Swartz, Prodr. Veg. Ind. Occ. 22. 1788. "India occidental-is." The 

 type, in the Swartz Herbarium, has already been discussed. a The sterile lemma 

 bears in its axis a well-developed palea. There is some uncertainty as to the original 

 locality of the type specimen of P. molle. It is said by Swartz to come from the West 

 Indies, but we have seen no other specimens of this species from that region. 



Panicum velutinosum Nees; Trin. Gram. Pan. 144. 1826. This is given as a syn- 

 onym of Panicum petiverii Trin. /?. Trinius's specimen was from "Brasil," commu- 

 nicated by "N. ab Esenb." This is in the Trinius Herbarium and is the original of 

 the plate & of P. velutinosum in the Icones. The spikelets differ from those of the type 

 of P. molle in that the palea of the sterile lemma is wanting. Nees^ later described 

 P. velutinosum, giving the locality as follows: "Habitat in sylvaticis prope Villa da 

 Cachoeira, provinciae Bahiensis." [Brazil]. His specimen, of which Trinius's is evi- 

 dently a duplicate, is in the Munich Herbarium. There are six plants on the sheet, 

 all much smaller than Swartz's plant, and having shorter, broader blades. The 

 Argentine specimens, which have been referred to P. velutinosum, have a well- 

 developed palea in the sterile floret. Doell^ recognized the two species as distinct 

 chiefly because of this character. More material is needed definitely to determine 

 whether or not these two forms should be segregated. 



In Kunth's Enumeration the name is misprinted P. velutinum Nees. 



DESCRIPTION. 



Plants ascending or spreading from a decumbent base, usually branching; culms 

 30 to 70 cm. high, softly pubescent, at least below the pubescent nodes; sheaths usu- 

 ally shorter than the internodes, loose, 

 softly pubescent between the nerves, 

 sometimes obscurely so, densely ciliate; 

 ligule a dense ring of hairs about 1 mm. 

 long; blades ascending or spreading, 4 to 

 15 cm. long, rarely longer, 7 to 15 mm. 

 wide, rounded at the base, finely and 

 softly pubescent on both surfaces or 

 nearly glabrous on the upper; panicles 

 short-exserted or, especially those of the 

 branches, included at base, 6 to 15 cm. 

 long, the several to many subracemose 

 branches ascending, rarely widely spread- 

 ing at maturity, the main axis and those 

 of the branches densely softly pubescent and also beset with stiff, spreading hairs 

 about 1 mm. long, the short pedicels of the somewhat crowded spikelets similarly 

 hirsute; spikelets 3.4 to 3.8 mm. long, 1.5 to 1.7 mm. wide, obovate, turgid, abruptly 

 pointed, short-attenuate at base, a distinct intemode of the rachilla between the 

 first and second glumes; first glume clasping, half as long as the spikelet or more, 

 acute, 5-nerved, the nerves usually anastomosing toward the apex, pilose; second 

 glume and sterile lemma pointed beyond the fruit, 5-nerved, obscurely reticulated 

 between the nerves, pilose, often densely so; fruit 2.6 to 3 mm. long, 1.5 to 1.6 mm. 

 wide, elliptic, apiculate. 



The Argentine specimens are less velvety and approach in appearance the large 

 forms of P. arizonicum, but these as well as the Mexican specimens lack the papillae 

 commonly present on the sheaths of P. arizonicum. 



a See footnote c, p. 36. c Agrost. Bras. 121. 1829. 



b Trin. Gram. Icon. 2 : pi. 180. 1829. d Mart. Fl. Bras. 2 2 : 187. 1877.. 



e Enum. PI. 1: 92. 1833. 



Fig. 23.— P. molle. From type specimen. 



