1922] Linder,—Some Varieties of Panicum virgatum 13 
var. breviramosum of Nash‘ differs from the new P. virgatum, var. 
thyrsiforme by having a much smaller panicle (9-13 cm. long, 3-5 em. 
wide) and shorter leaves. 
Ranging from southeastern Nova Scotia and near the coast from 
the lower Penobscot Valley to New Jersey and locally to central New 
York, is a variety which has been confused with both P. virgatum and 
its var. cubense. It is, however, readily separated from these by 
having, not the long scaly, creeping 
rootstock, but very numerous culms ris- 
ing from a stout multicipital caudex 
with very short internodes and with 
quickly ascending short basal offshoots. 
The shape of the spikelet in the cespitose 
plant differs from that of true P. virgat- 
um in that, owing to the spreading of the 
first glume (a habit which, however, is 
not constant), the spikelet looks blunt 
and squarish instead ofelongate. Again, 
the spikelet has a more constant length, 
ranging between 3.2 and 4 mm., the ma- 
jority being around 3.5 mm.; while the 
spikelets of typical P. virgatum range 
from 3.5 to 6 mm. in length. The panicle 
varies from open to quite close, just as in the true form of the 
Fig. 2. Base of var. spissum. 
species. 
The following key will give a more concise idea of the classification 
of the varieties here discussed: 
Plants with long, scaly, creeping rootstocks. 
Lower rays of panicle longer than middle ones. 
Spikelets 3.5-6 mm. long: palea shorter than second 
lume P. virgatum L. 
Spikelets 2.8-3.2 mm. long: palea and second glume 
subequal var. cubense Griseb. 
Lower rays of the panicle scarcely exceeding the middle ones. 
Blades 12-15 mm. broad, stiff, coriaceous: lemma 
rounded at tip: second glume short-mucronate: 
panicle ellipsoid var. scorteum. 
Blades 7-11 mm. broad, not stiff or coriaceous: lemma 
pointed: second glume tapering to subulate tip: 
panicle ellipsoid-cylindrical _ var. thyrsiforme. 
Plants with short, quickly ascending rootstocks, forming 
tussocks var. spissum. 
4 Bull. Torr. Bot. Club. 23: 150. 1896. 
