MANUAL OF THE GRASSES OF THE UNITED STATES 767 



T. FLORIDANTJM. 



but smaller, infolding the remainder of the spikelet; sterile lemma, 

 fertile lemma, and palea very thin and hyaline, these progressively 

 smaller. Robust perennials, with usually broad flat blades and 

 monoecious terminal and axillary inflorescences of 1 to 3 spikes, the 

 pistillate part below, breaking up into bony, seedlike joints, the 

 staminate above on the same rachis, deciduous as a whole. Type 

 species, Tripsacum dactyloides. Name of unknown origin, said by 

 some to come from Greek tribein, to rub, alluding to the smooth 

 joints. 



The species are good forage grasses, but even the more widely 

 spread T. dactyloides is not common enough to be of importance. 

 Two large species not found in the United States, T. laxum Nash and 

 T. latifoliwm Hitchc, of Central America, are occasionally cultivated 

 for forage in that region. The genus is of interest because it is related 

 to maize. A hybrid between T. dactyloides and maize has recently 

 been made. 10 



Staminate spikelets membranaceous, the members of the pair unequally pedi- 

 celed, one nearly sessile, the other with a distinct pedicel. 



3. T. LANCEOLATUM. 



Staminate spikelets rather chartaceous, both members of the pair nearly sessile. 

 Blades 1 to 2 cm wide, flat; plants 1 to 2 m tall; terminal spikes usually more 



than one 1. T. dactyloides. 



Blades 1 to 4 mm wide, subinvolute; plants less than 1 m tall; all spikes usually 



solitary 2 



1. Tripsacum dactyloides (L.) L. 



Eastern gamagrass. (Fig. 1692, A.) 



Plants in large clumps, with thick knotty 



rhizomes, 2 to 3 m tall or sometimes taller, 



glabrous throughout; blades usually 1 to 



2 cm wide, flat, scabrous on the 



margin; spikes 15 to 25 cm long, the 



pistillate part one-fourth the entire length 



or less, the terminal spikes usually 2 or 3, 



sometimes only 1, those of the branches 



usually solitary; pistillate spikelets 



7 to 10 mm long, the joints rhombic; stam- 

 inate spikelets 7 to 

 1 1 mm long, both of 

 a pair nearly sessile, 

 the glumes rather 

 chartaceous. Ql 

 — Swales, banks of 



Figure 1693— Distribution of Streams, and moist 



Tripsacum dactyloides. places, Massachu- 



setts to Michigan, Iowa, and Nebraska, 

 south to Florida and Texas; West 

 Indies and Mexico to Brazil (fig. 1693). 



2. Tripsacum floridanum Porter. 

 Florida gamagrass. (Fig. 1692, 

 B.) Smaller than T. dactyloides in all 

 ways, commonly less than 1 m tall; blades 

 mostly 1 to 4 mm wide; terminal and 

 axillary spikes usually solitary (rarely 2 

 or more). % — Low rocky pine lands, 

 southern Florida. 



Figure 1694. — Tripsacum lanceolaturri, 

 X 1. (Lemmon, Ariz.) 



«° Mangelsdorf, P. C, and Reeves, R. Q. Jour. Hered. 22: 329-343. 1931. 

 65974°— 35 49 



