MAXUAL OF THE GRASSES OF THE UNITED STATES 29 



TRIBE 14. TRIPSACEAE 



Spikelets unisexual, the staminate in pairs, or sometimes in threes, 

 2-flowered, the pistillate usually single, 2-flowered, the lower floret 

 sterile, embedded in hollows of the thickened articulate axis and fall- 

 ing attached to the joints, or enclosed in a thickened involucre or 

 sheath or, in Zea, crowded in rows on a thickened axis (cob); glumes 

 membranaceous or thick and rigid, awnless; lemmas and palea 

 hyaline, awnless. Plants monoecious. 



'This small tribe of seven genera is scarcely more than a subtribe 

 of Andropogoneae, differing chiefly in the total suppression of the 

 sterile spikelet of a pair, the fertile spikelet being pistillate only and 

 solitary: staminate spikelets paired. It is also known as Maydeae. 



Key to the genera of Tripsaceae 



Staminate and pistillate spikelet? in separate inflorescences, the first in a terminal 

 tassel, the second in the axils of the leaves. 

 Pistillate spikes distinct, the spikelets embedded in the hardened rachis, this 



disarticulating at maturity 158. Euchlaena. 



Pistillate spikes grown together forming an ear, the grains at maturity much 



exceeding the glumes 159. Zea. 



Staminate and pistillate spikelets in separate portions of the same spike, the 

 pistillate below. 

 Spikes short, the 1- or 2-flowered pistillate portion enclosed in a beadlike 



sheathing bract 156. Coix. 



Spikes many-flowered, the pistillate portion breaking up into several 1-seeded 

 joints; no beadlike sheathing bract 157. Tripsacum. 



DESCRIPTIONS OF GENERA AND SPECIES 



TRIBE 1. BAMBUSEAE 



1. ARUNDINlKIA Miehx. Cane 



Spikelets few- to many -flowered, large, compressed, the rachilla 

 disarticulating above the glumes and between the florets; glumes 

 unequal, shorter than the lemmas, the first sometimes wanting; 

 lemmas acute, acuminate, or mucronate, faintly many-nerved; palea 

 about as long as the lemma, prominently 2-keeled; stamens 6. 

 Shrubs or tall reeds, with woody perennial branching culms, flat 

 petiolate blades, articulate with the sheaths, and loose racemes or 

 panicles. Type species, Arundinaria macrosperma Michx. (A 

 gigantea.) Name from Latin Arundo, a reed. 



Panicles on leafy branches; culms as much as 10 m tall 1. A. gigantea. 



Panicles on leafless shoots from creeping rhizomes 2. A. tecta. 



1. Arundinaria gigantea (Walt.) Chapm. Southern caxe. (Fig. 

 1.) Culms as much as 10 m tall, erect from stout rhizomes; sheaths 

 bearing several bristles at the summit on each side, these disappear- 

 ing with age, the collar prominent, pubescent; blades oblong-lanceo- 

 late to linear-lanceolate, rounded to a somewhat cuneate petiole, 

 acuminate, finely tessellate with numerous cross veins, sharply 

 serrulate on the margin, 10 to 20 cm long, mostly 1 to 2 cm wide or on 

 vigorous shoots as much as 3 cm wide; flowering branchlets in 

 fascicles on the main culm or short branches, their sheaths bladeless 

 or nearly so, the racemes or simple panicles 1- to several-flowered; 

 spikelets 3 to 7 cm long, mostly 8- to 12-flowered; glumes distant; 

 lemmas pubescent, at least toward base, or glabrescent, acuminate, 

 about 2 cm long. 2/ (A. macrosperma Michx.) — Growing in colonies, 



