GRAMI^'EAE (GRASS FAMILY) 87 



Subfamily I. PANICOfDEAE 



Spikelets 1-, rarely 2-flowered, when 2-flowered the terminal flower perfect, 

 the lower staminate or neuter ; rhachilla articulated below the glumes, the more 

 or less dorsally compressed spikelets falling from the pedicels entire, singly, in 

 groups, or together with joints of an articulate rhachis. 



This first grand division of the Gramineae is based upon two characters in 

 combination, the articulation of the pedicels just below the spikelets or cluster 

 of spikelets and the single perfect flower^ which may or may not have a staminate 

 or imperfect flower below it. The lemma of the imperfect flower is similar to 

 the glumes in texture in Paniceae and like the fertile lemma in the other tribes. 

 In a few genera the first glume is obsolete, but in these cases the articulation 

 helow the dorsally compressed spikelets indicates their relation. 



Tribe I. MAYDEAE. Pistillate and staminate spikelets in different inflorescences or in different 

 parts of the same inflorescence ; a.vnless ; glumes indurated. 



1. Tripsacum. Staminate spikelets above the pistillate, in pairs at each joint of a spike-like 



raceme ; pistillate single, imbedded in the jointed rhachis. 



Tribe II. ANDR0P0G6nEAE. Spikelets in pairs or threes on the usually articulate rhachis of a 

 spike like raceme, one sessile and fertile, the other pediceled and perfect, staminate, neuter or 

 rudimentary ; glumes more or less indurated ; lemmas smaller and hyaline, that of the fertile 

 flower usually awned. 



2. Rottboellia. Rhachis naked ; pediceled spikelets neuter, often rudimentary; fertile spikelets 



awnless. 



3. Erianthus. Rhachis hairy ; spikelets all perfect and fertile, awned. 



4. Andropogon. Rhachis hairy ; pediceled spikelets sterile, often rudimentary ; fertile spikelets 



awned. 



5. Sorghastrum. Racemes reduced to one or two joints, on slender peduncles, arranged in 



open panicles ; second spikelet reduced to a pedicel. 



Tribe III. PANf CEAE. Spikelets all perfect (in our genera) in racemes or panicles ; glumes mem- 

 branaceous, unequal, the first usually small, sometimes obsolete ; a lemma of like texture, 

 empty or Avith a hyaline palea, rarely inclosing a staminate flower, subtends the perfect floret 

 and simulates a third glume ; fertile lemma and palea indurated, firmly clasped together, 

 inclosing tho free grain, awnless (pointed in Echinochloa). 



* Spikelets without an involucre of bristles. 



■^ Lemma leathery-indurated with hyaline margins not inrolled ; spikelets lanceolate; first 



glume sometimes wanting. 



6. Digitaria. Spikelets in slender spike-like racemes, aggregated toward the summit of the 



culm. 



7. Leptoloma. Spikelets long-pediceled in a diffuse panicle. 



+- +- Lemma chartaceous-indurated ; margins not hyaline, inrolled except in Amphicarpon, 



++ Glumes and lemmas awnless. 



8. Amphicarpon. Spikelets of 2 kinds, one in terminal panicle, not fruitful ; the other sub- 



terranean, perfecting fruit ; margins of lemma not inrolled. 



9. Paspalum. Spikelets all alike, plano-convex, sessile or nearly so, solitary or in pairs in 2 



rows on one side of a flattened rhachis ; first glume obsolete (rarely present) ; spikelets 

 placed with back of fertile lemma toward the rhachis. 



10. Axonopus. Spikelets all alike, compressed, biconvex, sessile, solitary in 2 rows on one side 



of a flattened rhachis ; first glume obsolete ; spikelets placed with the back of the fer- 

 tile lemma from the rhachis. 



11. Panicum. Spikelets all alike, biconvex, in panicles (rarely racemes); first glume present; 



second glume and sterile lemma similar. 



12. SacciolepiS. Spikelets all alike, in spike-like panicles ; second glume saccate at base. 



11-nerved ; sterile lemma flat, 8-5-nerved. 



