Part 7 - UNC Herbarium

POACEAE 862
sheaths. Nodes with short pubescence generally are not regarded as bearded. Lower nodes are more likely to be bearded than
upper nodes. When analyzing sheaths, look at those on the lower half of the culm. Senescent vernal sheaths often lose their
pubescence (though in some species hair papillae are evident). All references in the key to sheath glabrousness or pubescence is
without regard to the presence or absence of marginal hairs (cilia). A sheath that is glabrous except for marginal cilia is called
glabrous. All culm leaves should be analyzed for blade characters; in general, the key relies on the size and character of the
vernal blades. A "cordate" blade is one where the basal lobes of the blade extend outward and partially surround the culm when
the culm is enclosed by the sheath. As with sheaths, references in the key to blade glabrousness or pubescence is without regard
to marginal cilia. The ligule is an important diagnostic character for many Dichanthelium taxa; at least three ligules per specimen
should be examined before making conclusions about its structure and length. Ligules form a distinct ring from a cartilaginous
base at the inner summit of the sheath; in some species the ligule is membranous, but in most it is pubescent. Care must be taken
to distinguish the pubescence of the ligule from any pubescence emanating from the inner surface of the blade base, and from
marginal cilia. Ligules of senescent vernal leaves frequently lose their integrity. Spikelet shape as well as length should be
determined only from mature spikelets. Measure the length from the base of the first glume (usually at an articulation) to the
apex of the second glume or sterile lemma (whichever is longer). A micrometer is essential for determining the length of
spikelets, first glumes, ligules, and various pilosity features. Sometimes one-tenth of a millimeter is all that separates two
Dichanthelium taxa.
Certain characters, particularly node bearding, cordate/non-cordate blade bases, and ligule length, can be quite variable, and an
effort has been made to account for this variability in the key. Nonetheless, some specimens just won't "fit," and the road not
taken may have to be reconsidered.
References: Gould and Clark (1978)=Z; Freckmann (1981)=Y; Lelong (1984)=X; LeBlond (2001)=Q; Davidse and Polh (1992);
Hansen & Wunderlin (1988); Hitchcock & Chase (1910); Freckmann & Lelong (2002). The treatment of Dichanthelium sect.
Lanuginosa (=D. acuminatum group) is based closely on Y. The contributor must take responsibility for the treatment of sect.
Angustifolia (including D. hirstii), sections Dichotoma and Ensifolia (the D. dichotomum group), and for sect. Lancearia. Other
treatments are based largely on Z.
1 Plants densely tufted, often cushion-forming; leaves basally disposed, the blades ascending or spreading-ascending, not
forming a distinct rosette of basal leaves shorter than the culm leaves; autumnal culms branching basally or from the lower
nodes.................................................................................................................................................................................Key A
1 Plants less densely or sparsely tufted, not cushion-forming; leaves well-distributed on the culm, usually much longer than
the short, often broad and spreading basal rosette leaves; autumnal culms usually branching from the mid and upper nodes.
2 Spikelets 3.3-5.2 mm long ........................................................................................................................................Key B
2 Spikelets 0.8-3.2 mm long.
3 Spikelets 2.1-3.2 mm long.
4 Larger culm blades 13-25 mm wide..........................................................................................................Key C
4 Larger culm blades < 13 mm wide.
5 Culm nodes (at least the lower) bearded............................................................................................Key D
5 Culm nodes not bearded, the lowermost sometimes puberulent or sparsely hairy.............................Key E
3 Spikelets 0.8-2.0 mm long.
6 Lower culm internodes variously hairy..................................................................................................... Key F
6 Lower culm internodes glabrous .............................................................................................................. Key G
Key A - Plants densely tufted, often cushion-forming; leaves basally disposed,
the blades ascending or spreading-ascending,
not forming a distinct rosette of basal leaves
shorter than the culm leaves;
autumnal culms branching basally or from the lower nodes
1 Spikelets 2.4-4.5 mm long.
2 Nodes, internodes, and sheaths glabrous; blades 4-13 cm, 5-8 mm, the surfaces smooth, glabrous; spikelets 2.4-2.9 mm
long, glabrous; not known to produce axillary (autumnal) inflorescences ...................................................[D. nudicaule]
2 Nodes bearded or otherwise pubescent; internodes and sheaths variously pubescent to glabrate; blades 6-35 cm, 2-5
mm, one or both surfaces scabrous and often pubescent; spikelets 1.7-4.5 mm long, glabrous or pubescent; plants
produce axillary (autumnal) inflorescences.
3 Spikelets 2.8-3.8 (-4.5) mm long, the second glume and sterile lemma pointed or beaked and extended beyond the
summit of the fertile lemma; first glume 1.2-2 mm long................................................................. D. depauperatum
3 Spikelets 1.7-2.8 mm long, the second glume and sterile lemma blunt or broadly pointed, not extending beyond
the summit of the fertile lemma; first glume 0.7-1.2 mm long.......................................................... D. linearifolium
1 Spikelets 0.9-2.3 mm long.
4 Longer blades > 6 cm; if only 6 cm, then sheaths retrorsely long-pilose (D. laxiflorum).
5 Spikelets 1.2-1.5 mm long, glabrous...................................................................[D. dichotomum var. glabrifolium]
5 Spikelets 1.7-2.3 (-2.8) mm long, pubescent.