108 Bulletin V. 2. 



The arrangement of the spikelets upon the stem constitutes 

 what is termed the inflorescence^ or what we often hear erroneously 

 called the "head." If that portion of the main axis or stem which 

 bears the spikelets is unbranched so that these are sessile (i. e., 

 without pedicels), the inflorescence is a true spike^ e. g., wheat, 

 rye-grass; when the main axis is branched, each branch forming a 

 pedicel to a single spikelet, the inflorescence is a raceme. This 

 form is not common. Usually the primary branches branch again 

 and again, resulting in the formation ot a panicle. The panicle 

 may be open or widely spreading, as in oats or in Kentucky blue- 

 grass; or, if the branches are very short, it may be narrow and 

 spike-like as in timothy or in meadow fox-tail. All gradations 

 of form between these two extremes occur. 



Key to the Genera of the Native and Cultivated Grasses of 



Tennessee. 



The numbers tcJ the right refer to the numbers at the left. 



I. Spikelets one- rarely two-flowered (when two-flowered the 

 second or terminal flower is perfect, the one below being 

 either staminate or neuter,) falling from the pedicels entire, 

 or together with certain joints of the rachis. (Series A. 

 PANICACE^.) 2 



1. Spikelets one- to many-flowered (when more than one-flower- 



ed the imperfect flower, if any, is uppermost,) lower empty 

 glumes usually remaining after the fall of the fruiting 

 glumes. (Series B. POACE^.) i6 



2. Spikelets terete or flattened on the back 3 



2. Spikelets strongly flattened laterally (Tribe Oryze^) 14 



3. Spikelets all unisexual, plants monoecious (Tribe Mayde.^.) , . 4 



3. Spikelets hermaphrodite, or staminate and hermaphrodite, 



the former standing near the latter 6 



4. Pistillate and staminate spikelets each in a separate inflor- 



escence, the former axillary, the latter terminal 5 



4. Pistillate and staminate spikelets in the same inflorescence, 



the axis of the former articulated between each spikelet. 

 (See Fig. n.) 3. Tripsacum. 



5. Pistillate spikes distinct, fasciculate, their axes articulated 



(See Fig. 32.) ... 1. Euchlaena. 



5. Pistillate spikes grown together forming a compound, con- 



tinuous and much thickened axis (the "cob."). .. 2. Zea. 



6. Axis of the inflorescence articulated (continuous in the cul- 



tivated Miscanthus,) flowering glume hyaline (Tribe An- 



DROPOGONE^.) 7 



6. Axis of the inflorescence continuous, flowering glume in- 

 durated or firmer in texture than the empty glumes (Tribe 



PANICEiE) 10 



