GRASSES OF IOWA. 



a. Hilum punctiform. Spikelets not flattened laterally, but usually some- 

 what dorsally compressed or else perfectly round. 



I. Flowering glumes and palea (the latter often wanting) hyaline- 

 Empty glumes thick membranaceous to coriaceous or cartilaginous, the 

 lowest the largest with its edges embracing the others- Spikelets gen- 

 erally in racemes or spikes whose articulate axes break up at maturity. 



i- Staminate and pistillate spikelets in separate inflorescences or 

 en different parts of the same inflorescence I. MAYDEAE. 



2. Spikelets either all perfect, or staminate and perfect, and so 

 arranged in the same inflorescence that a staminate stands near a 

 perfect II. ANDROPOGONEAE. 



II. Flowering glumes and palea membranaceous; empty glumes, 

 herbaceous, chartaceous or coriaceous, the first generally the largest; 

 spikelets falling off singly or in groups from the continuous rachis. 



—III. ZOYSIEAE. 



III. Flowering glume and palea membranaceous, empty glumes, 

 herbaceous or chartaceous; the first empty glume smaller or narrower 

 than the following ones. Spikelets falling off singly from the ultimate 

 branches cf the panicle IV. TRISTEGINEAE. 



IV- Flowering glume and palea cartilaginous, coriaceous or char- 

 taceous. Empty glume more delicate, usually herbaceous, the first usually 

 smaller. Spikelets falling off singly from the ultimate branches of the 

 panicle or continuous (rarely articulate) rachis of a spike- 



—V. PANICEAE. 



b. Hilum linear, spikelets laterally compressed ..VI. ORYZEAE- 



B. Spikelets i-many-flowered, the i-flowered frequently with the rachilla 



produced beyond the flowers, rachilla generally articulated above the empty 

 glumes, so that these remain after the fall of the fruiting glumes. When from 

 two to many-flowered there always are distinct internodes between the flowers. 



a- Culm herbaceous, annual ; leaf-blade sessile, not articulated with 

 the sheath. 



Spikelets upon distinct (sometimes very short) pedicels, in panicles, 

 spike-like panicles, or racemes (without notches in the main axes). 

 I. Spikelets one-flowered: 



i. Empty glumes four, palea one-nerved. 



—VII. PHALARIDEAE. 

 2. Empty glumes two (rarely none), palea two-nerved. 



—VIII. AGROSTIDEAE. 

 II. Spikelets 2-many-flowered : 



i. Flowering glume generally shorter than the empty ones; 

 usually with a bent awn on the back, rarely awned from the point or 

 awnless. When not awned there are two nearly opposite florets, and 



the rachilla is not produced beyond them IX- AVENEAE. 



2- Floral glume generally longer than the empty ones, unawned 

 or with a straight awn from the point (seldom below). 



—XI. FESTUCEAE 



Spikelets crowded in two close rows, forming a one-sided spike or raceme 



with a continuous axis X. CHLORIDEAE.. . 



