Part 7 - UNC Herbarium

POACEAE 898
2 Leaves primarily basal or low-cauline, 2-4 (-5) dm long, 4-10 mm wide; inflorescence a raceme or a racemiform
panicle; culms prostrate, the upper leaves very reduced, often merely bladeless sheaths ............................. O. asperifolia
2 Leaves primarily cauline, 1-2.5 dm long, 8-15 mm wide; inflorescence a panicle; culms erect, the upper leaves welldeveloped...........................................................................................................................
[see Piptatherum racemosum]
Oryzopsis asperifolia Michaux, Rough-leaved Ricegrass, Whiteseed Mountain-ricegrass. Mt (VA): high elevation pineoak/heath
barrens and woodlands; rare (VA Rare). Newfoundland west to British Columbia, south to w. VA, WV, n. IN, SD,
NM, and UT. This grass forms large cespitose clumps, the leaves evergreen and somewhat bicolored (green on the upper surface,
bluish on the lower). [= C, F, G, HC, K]
Panicum Linnaeus 1753 (Panic Grass)
(also see Dichanthelium, Phanopyrum, Setaria, Steinchisma, and Urochloa)
(contributed by Richard J. LeBlond)
{INTRODUCTION: Describe differences between Panicum, Dichanthelium, Urochloa (=Brachiaria), and Paspalidium (now in
Setaria), all of which are treated as Panicum in RAB. Describe collection methods and character analysis.}
There has been considerable controversy over the generic limits of Panicum. In its broader recent conceptions, it has been
considered to include (in our area) taxa sometimes and variously segregated as Brachiaria, Dichanthelium, Eriochloa,
Paspalidium, Phanopyrum, Steinchisma, and Urochloa. All were originally recognized based on morphological characteristics,
to which have recently been added anatomical, chemical, and other evidence. Crins (1991) recognizes Eriochloa, Urochloa
(including Brachiaria), Paspalidium, and Panicum as genera, with Panicum subdivided into subgenera Panicum, Agrostoides,
Dichanthelium, Phanopyrum, and Steinchisma. We prefer to recognize most of the segregates as genera, pending further
analyses, since there is little evidence that these groups are more closely related to one another than they are to other genera
recognized in the Paniceae. Phanopyrum and Dichanthelium are the only segregate groups with C 3 photosynthesis. Eriochloa
and Urochloa (including Brachiaria) have C 4 photosynthesis, with PEP-ck decarboxylation. Panicum and Setaria (Paspalidium)
have C 4 photosynthesis, with NAD-me or NADP-me decarboxylation. Steinchisma, in addition to its unusual expansion of the
palea, apparently has a peculiar photosynthetic pathway, described by Crins (1991) as "intermediate between" C 3 and C 4
photosynthesis; "the leaves have Kranz anatomy, but there are fewer organelles than usual in the outer sheath."
We agree with Hansen & Wunderlin (1988) that "Dichanthelium is as 'good' a grass genus as many others (e.g. Brachiaria,
Sacciolepis, and many more in other tribes)." Despite arguments to the contrary, there is little doubt that Dichanthelium is a
natural group. Zuloaga, Ellis, and Morrone (1993) argue against the recognition of Dichanthelium as a genus, preferring to treat
it as a subgenus under Panicum. They state, however, "within Panicum, Dichanthelium can be distinguished at the subgeneric
level by the following set of characters: lax inflorescences; ellipsoid to obovoid spikelets; upper glume and lower lemma usually
7-11 nerved; upper anthecium apiculate or shortly crested, and simple papillae on the lemma and palea. Anatomically, all species
are non-Kranz or C 3 , with the outer parenchymatous sheath lacking specialized chloroplasts", etc. The argument that
Phanopyrum also has C 3 photosynthesis does not materially affect the issue of the taxonomic rank at which to recognize the
groups.
We also agree with Hansen & Wunderlin (1988) that "the acceptance of Dichanthelium provides a more consistent generic
classification." It offers conveniences, as well, in our area, where Dichanthelium and Panicum are readily distinguishable from
each other, and the combined genus would be very large, indeed. References: Lelong (1986)=Z; Zuloaga & Morrone (1996)=Y;
Freckmann & Lelong in FNA (2003a).
1 Spikelets tuberculate ............................................................................................................................................P. verrucosum
1 Spikelets smooth, not tuberculate.
2 First glume 5-7.5 mm long, nearly as long as sterile lemma; fertile lemma 1/3 length of sterile lemma ............................
............................................................................................................................................. [Phanopyrum gymnocarpon]
2 First glume shorter, or if this long, then at most 3/4 length of sterile lemma; fertile lemma > ½ the length of the sterile
lemma.
3 Sterile palea indurate and expanding the spikelet at maturity, as long as sterile lemma; outer surface of the distal
palea with compound papillae.....................................................................................................[Steinchisma hians]
3 Sterile palea membranous, not expanding the spikelet at maturity, usually shorter than sterile lemma or absent;
outer surface of the distal palea lacking compound papillae.
4 Panicle < 2 cm wide at maturity.
5 Spikelets >4.5 mm long; first glume > 2.4 mm long; ligule 4-6 mm long; [of coastal dunes]; [subgenus
Panicum, section Repentia]................................................................................. P. amarum var. amarum
5 Spikelets < 4 mm long; first glume < 2.1 mm long; ligule < 2 mm long; [not of coastal dunes].
6 Blades involute, 1.5-4 mm wide; culms wiry; [subgenus Agrostoides, section Tenera]......................
........................................................................................................................................... P. tenerum
6 Blades flat, the larger 6-20 mm wide; culms stout.