714 MISC. PUBLICATION 200, U. S. DEPT. OF AGRICULTURE 



138. AMPHICARPUM Kunth 



{Amphicarpon Raf.) 



Spikelets of two kinds on the same plant, one in a terminal panicle, 

 perfect but not fruitful, the other cleistogamous on slender leafless 

 subterranean branches from the base of the culm or sometimes also 

 from the lower nodes; first glume of the aerial spikelets variable in 

 size, sometimes obsolete; second glume and sterile lemma about 

 equal; lemma and palea indurate, the 

 margins of the lemma thin and flat; 

 fruiting spikelets much larger, the 

 first glume wanting; second glume 

 and sterile lemma strongly nerved, 

 subrigid, exceeded at maturity by the 

 turgid, elliptic, acuminate fruit with 

 strongly indur- 

 ate lemma and 

 palea, the mar- 

 gins of the lem- 

 ma thin and 

 flat; stamens 

 with small an- 

 thers on short 

 filaments. An- 

 nual or perennial erect grasses, with 

 flat blades and narrow terminal pani- 

 cles. Type species, Milium amphicar- 

 pon Pursh (Amphicarpum purshii). 

 Name from Greek amphikarpos, doubly 

 fruit-bearing, alluding to the two kinds 

 of spikelets. 



Blades conspicuously hirsute 1. A. purshii. 



Blades glabrous or nearly so 2. A. muhlenbergianum. 



1. Amphicarpum purshii Kunth. (Fig. 1597.) Annual; culms 

 erect, 30 to 80 cm tall, the leaves crowded toward the base, hirsute; 

 blades erect, 10 to 15 cm long, 5 to 15 mm wide, sharp-pointed; 

 panicle 3 to 20 cm long; spikelets elliptic, 4 to 5 mm long; subterra- 

 nean spikelets 7 to 8 mm long, plump, acuminate. © (Amphicarpon 

 amphicarpon Nash.) — Sandy pinelands, New Jersey to Georgia (fig. 

 1598). 



2. Amphicarpum muhlenbergianum (Schult.) Hitchc. (Fig. 1599.) 

 Perennial; culms usually decumbent at base, 30 to 100 cm tall; leaves 

 evenly distributed; blades firm, white-margined when dry, mostly less 

 than 10 cm long, 5 to 10 mm wide; panicle long-exserted, few-flowered; 

 spikelets narrowly lanceolate, 6 to 7 mm long; subterranean spikelets 

 6 to 9 mm long. % (A. floridanum Chapm.) — Low pinelands, 

 South Carolina and Florida. 



Figure 1598.— Distribution of 

 Amphicarpum purshii. 



Figure 1599.— Amphicarpum muhlenbergi- 

 anum, X 1. (Chapman, Fla.) 



