Andropogon, Bothriochloa, Dichanthium, Schizachyrium
Schizachyrium is similar to Andropogon but differs by having the ultimate inflorescence axes (racemes or rames of some authors) single rather than paired. Also similar, Bothriochloa pertusa has a conspicuous pit on each spikelet. Dichanthium is under 1 m tall, has the rames clustered at the top of the plant, and often has awns > 16 mm long (which is rare in Andropogon).
1. Spikelets with a conspicuous gland or pit
(visible with a hand lens) on the lower glume…
(Spikelets 3-4 mm long; awn 10-17 mm long)
1. Spikelets glandless…2
2. Ultimate branches of the inflorescence (rames) single, zig-zag...10
2. Rames paired...3
3. Plants < 1 m tall; rames confined to top, awns often > 20 mm long...Dichanthium
3. Plants usually > 1 m tall (with exceptions; see "6" below); rames not confined to the top; awns usually < 16 mm long...4
4. Peduncles exposed, curved or drooping; ultimate
inflorescence branches (rames) < 2.1 cm long…...
4. Peduncles hidden, or exposed and straight; rames of variable lengths, usually (but not always) exceeding 2.1 cm long...5
5. Sessile spikelets usually (4.5)5-8.4 mm long. Pedicellate spikelets well developed …
(plants
usually in dry pine woods, with few [easily counted] inflorescence units
[vs. crowded and numerous in A. floridanus], rames 3-6 cm,
on long exposed straight peduncles; anthers 3;
awns to 25 mm)
5. Sessile spikelets usually < 4.5 mm long. Pedicellate spikelets absent or vestigial…6
6. Plants < 1 m tall...7
6. Plants > 1 m tall (there may be small individuals in a population generally > 1 m tall)...8
7. Inflorescence with expanded sheath(s) (inflated
and out of proportion to the small size of the plant). Leaf
blades and sheaths usually glabrous. Rames 2.8-4.2 cm long, usually
exserted on peduncles 5-31 mm long. Ligule 0.3-1.5 mm...
7. Inflorescence sheath not expanded; leaf blades
and sheaths usually pubescent. Rames 1.8-2.6 cm long, usually included
or the peduncle < 4 mm...
8. Peduncles often > 14 cm. Inflorescence
branches (rames, racemes) 2.5-3.7 cm long. Usually in scrub.
Inflorescence units numerous and crowded...
8. Peduncles usually < 14 cm. Rames 1.7-2.8 cm long...9
9. Inflorescence highly branched
and dense. Ligules 0.6-2.2 mm, ciliate. Sheaths usually scabrous, < 2 mm
wide.....
9. Inflorescence usually
diffuse, not a dense mass at the top of the plant. Ligules 0.1-1 mm,
membranous to sometimes ciliate. Sheaths usually smooth, > 2 mm wide...
10. Lower glume pubescent or glabrous. Upper glume cleft for
> half its length. Awn on sessile spikelet 15-25 mm….
10. Lower glume glabrous. Upper glume cleft for< half its length; awn on sessile spikelet < 17 mm...11
11. Awns on pedicellate spikelet absent-4 mm.
Blade
1.5-9 mm…
11. Awns on pedicellate spikelet to 1 mm. Blade 1-6 mm wide…S. rhizomatum (syn. of S. scoparium in Wunderlin)
|
|
Size |
Blades |
Leaf Sheaths |
Peduncle |
Sessile Spikelet |
Awn |
Anthers |
Ligule |
Rames |
Other |
|
A. brachy-stachyus |
> 1 m, can be 9' |
To 54 cm X 6 mm |
Smooth |
Usu. 20-31 mm |
Usu. 4.4-4.6 mm |
Short: 2-10 (11) mm |
1 |
Short: 0.2-0.5 mm |
Short: 1.5-2.1 cm |
Wet sites
Branches long and curved
|
|
A. floridanus |
> 1 m |
To 61 cm X 5 mm |
Scabrous or smooth |
Very long: Usu. 19-48 mm
> 31 mm unique |
Usu. 4-4.8 mm |
5-15 mm |
Usu. 1 |
0.4-1.2 mm |
Large: 2.5-3.7 cm (see also A. ternarius and A. gyrans) |
Scrub, dunes
|
|
A. glomeratus |
> 1 m, can be up to about 9' |
Can be the largest: To 109 cm X 9.5 mm.
> 60 cm unique > 6 mm wide unique |
Usu. scabrous |
Usu. 6-14 mm |
Usu. 3-5 mm
< 3.5 mm unique |
6-19 mm |
Usu. 1 |
May be large: 0.6-2.2 mm
> 1.5 mm unique |
1.7-2.5 cm |
Inflorescence usu. fan-shaped
Spathes usu. < 2 mm wide (vs. > 2mm in A. virgnicus)
|
|
A. gyrans |
< 1 m |
To 48 cm X 5 mm |
Smooth |
Usu. 5-31 mm |
Usu. 3.9 – 4.7 mm |
8-24 mm |
1 |
0.3-1.5 mm |
2.8-4.2 cm
> 3 cm unusual in other species except A. ternarius |
Scrub
Expanded inflorescence sheaths |
|
A. longiberbis |
< 1 m |
To 50 cm X 5.5 mm |
Smooth |
3-4 mm (rames not exserted) |
Usu. 4.1-4.5 mm |
10-21 mm |
1 |
Short: 0.2-0.6 mm
|
1.8-2.6 cm |
Especially pubescent species: leaves, inflorescence |
|
A. ternarius |
> 1 m |
To 3 mm wide |
Smooth, scabrous, or hairy |
Long: 5-20 cm |
Huge: 4.5-8.4 mm |
10-25 mm |
3 |
0.4-1.5 mm |
3-6 cm
> 3 cm unusual in other species except A. gyrans and A. floridanus |
Dry woods |
|
A. virginicus |
> 1 m |
To 52 cm X 6 mm |
Smooth or scabrous |
Usu. 4-6 mm (shorter than A. glomeratus) |
Usu. 3.5-3.8 mm |
6-21 mm |
Usu. 1 |
0.2-1 mm |
1.7-2.8 cm |
Spathes usu. > 2 mm wide (vs. narrower in A. glomeratus)
|