46 American Midland Naturalist Monograph No. 2 



1. LiMNOBlUM Rich. — Frogbit 



L. spongia (Bosc) Steud. Shallow water and mud, rare. Union Co. June- 

 Aug. 



2. Vallisneria L. — Eelgrass 



V. americana Michx. Wild Celery. Ponds and slow streams, mostly in the 

 n. half of the state. July- Aug. [K. spiralis sensu auth., not L.] 



3. Anacharis Bab. & Planch. — Waterweed 

 {Elodea sensu Michx., non Juss.) 



1. Leaves elliptical or oblong, obtuse, 1.2-4 mm. wide; slow streams, widely 

 distributed. July-Aug A. canadensis (Michx.) Planch. 



1. Leaves linear, acute, 0.7- L8 mm. wide; ponds and slow streams. July-Aug. 

 A. occidentalis (Pursh) Vict. 



22. Gramineae Juss. — Grass Family 



KEY TO THE TRIBES 



1. Plants woody; stems perennial Tribe 1. Bambuseae 



1. Plants herbaceous; stems annual. 



2. Spikelets 2-many-f lowered (except Hordeum and some Chlorideae). 

 3. Inflorescense a panicle, this sometimes contracted and spike-like. 



4. Lemmas longer than the glumes, awnless or with a straight apical awn 



Tribe 2. Feskiceae 



4. Lemmas usually shorter than the glumes, usually with a bent awn arising from 



the back Tribe 4. Aveneae 



3. Inflorescence of solitary, racemose, or digitate spikes or racemes, the spikelets 

 sessile or nearly so. 



5. Spikelets solitaiy, or in clusters of 2-6, arranged alternately on opposite sides 



of the axis; spike solitary, terminal Tribe 3. Horaeae 



5. Spikelets in one-sided spikes or racemes, the spikes or racemes solitary or 



several Tribe 6. Chlorideae 



2. Spikelets with only one perfect flower. 



6. Inflorescence not monoecious; flowers all perfect, or perfect and staminate or 

 neutral. 

 7. Glumes present; stamens 3 or L 

 8. Glumes 2. 



9. Spikelets in pairs, one sessile and fertile, the other pedicelled and stam- 

 inate or neuter, or rarely absent or reduced to a pedicel ; rachilla 

 articulated below the glumes Tribe 10. Andropogoneae 



9. Spikelets not in pairs; rachilla disarticulating above the glumes 



Tribe 5. Agrostideae 



8. Glumes apparently more than 2 (except Paspalum). 



10. Glumes apparently 4, the second and third being sterile lemmas present 



below the fertile floret Tribe 7. Phalarideae 



10. Glumes apparently 3, the third being a sterile lemma, the two real glumes 



very unequal Tribe 9. Paniceae 



7. Glumes obsolete or minute Tribe 8. Orvzeae 



6. Inflorescence monoecious, the staminate and pistillate flowers in different parts 

 of the same spike, or in different inflorescences, the staminate above the 

 pistillate ones Tribe I 1. Tripsaceae 



Tribe L Bambuseae. — Bamboo Tribe 



One genus 1. Anmdinaria 



