@ 2 Plat face of the perigynium s 
is either veinless or with 
Abd sae 5 short veins at the 
base 
2Y Rounded face of the perigynium 
6 ‘ veinless or with 2-3 weak 
y | indistinct veins 1§-Ce Preslii 
«</ Rounded face of the perigynium 
.¢ with 5-9 distinct veins 
+¢ Per um walls thin and 
membPanous, tending to 
remain green and contrasting 
ZO with the brown scales,thus 
giving the cluster a var- 
iegated appearance; flat 
ace veinless 17. Gs festivella 
+6 Perigyniun walls firm, 
tending to assume about 
the same color as the 
scales, the clusters thus 
3°\ more or less uniform in 
id color; flat face usually 
qi) with 2-3 incamplete veins 
at the base Zo. Ge pachystachya 
I> GbAt least same clusters within each clump bearing 
. { bracts which are nearly as long as the cluster 
a ee longer 
e = 
/€ Achenes 4-4.5 mm. long, clearly 5<veined on both 
2Asurfaces 15. Ge tribuloides 
/& Achenes 3.5 mm. long, faingly 35-5-veined on the 
29-rounded, veinless on the flat surface 240+ arthrostachya 
a 
' 
10 Sb Spikes small and often subglobose,more or less separated and 
44 distinct, the lowermost usually remote; culms mostly filiform 
/~ Leaves 2-5 mm. wide, usually as long as the culms or longer, 
1, soft and grasslike; perigynia mostly appressed 
'/ Perigynia 3.5-4 mm. long, the beak about 1/3 as long as the 
/$ body 22.C» leptopoda 
(Y Perigynia 4-4.5 mn. long, the beak abot 1/2 as long as 
|¢ the body 29.C.- Bolanderi 
c jv Leaves 1-2 mn. wide, usually shorter than the culms; perigy- 
/|, nia mostly spreading 
