Panicum capillare
 
Witch-Grass

Spikelet - Parts Spread Apart

Hudson Bay, SK
24-August-2023

The parts of this spikelet were manually spread apart.  Note the spikelet is less than 4 mm long and lacks bristles. The lower glume is longer than 1/5 the length of the spikelet.  The upper glume and lemma of the sterile floret are glabrous and the lemma of the sterile floret is unawned.

The following items are taken from keys in Flora of Saskatchewan, Fascicle 4, Grasses of Saskatchewan by Anna L. Leighton and Vernon L. Harms.  Family Poaceae is first divided into tribes, then the tribes are divided into genera, and the genera divided into species.  However, there are a number of tribes that are very difficult to distinguish morphologically.  These are grouped into a large, artificial tribe I call "Multitribe".  Multitribe is then divided into groups, and each group is then divided into genera.  The answers are in the order you would normally work through the keys.

Paniceae: Answers to key questions leading to this tribe. 
Mature inflorescence, if breaking into units, then the units not as below; NOT [Mature inflorescence breaking into spikelet units consisting of a sessile fertile spikelet, a hairy pedicel with or without a sterile spikelet at tip, and a hairy rachis joint, all arising at the same point (a node) in specialized panicle branches called rames]
Spikelets usually dorsally compressed, appearing 1-flowered but containing 1 fertile floret and 1 sterile floret, the latter attached to the base of fertile floret opposite the upper glume, resembling the upper glume, and together with the upper glume enveloping the fertile floret; lower glumes minute (sometimes absent) to 3/4 as long as upper glumes and typically wrapping most of the way around the pedicel at base; fertile floret seed-like with chartaceous-indurate lemma and palea enclosing flower and fruit; disarticulation below the glumes with rare exceptions; NOT [Spikelets not as above; sterile florets if present, either located distal to the fertile floret(s) on the rachilla or paired and attached at the base of a single fertile floret, not paired with the upper glume as above; lemma and palea variously textured, enclosing the flower or not; disarticulation usually above the glumes]

Panicum: Answers to key questions leading to this genus (in tribe Paniceae). 
Spikelets lacking bristles but rachis and pedicels may have scattered, long, papillose-based hairs; panicle not spike-like; NOT [Spikelets with bristles attached in groups at base; panicle dense and spike-like]
Lemma of sterile florets unawned; ligules present; panicle branches not as below; NOT [Lemma of sterile florets often awned; ligules absent; panicle branches lateral, densely-flowered and spike-like]
Panicle branches not as below; ligules membranous and ciliate, or consisting entirely of hairs; lower glume >= 1/5 length of the spikelet, always present; NOT [Panicle branches attached near tip of culm, spike-like, flattened and wing-margined with spikelets borne in groups of 2-3 (5) in 2 rows along the axis on the abaxial side of branch; ligule membranous, not ciliate; lower glume a minute triangle or a rounded membranous flap < 1/5 length of the spikelet, or absent]
Upper glume and lemma of sterile floret glabrous; basal leaves similar to culm leaves, not forming a basal rosette; NOT [Upper glume and lemma of sterile floret pubescent; basal leaves usually different from the culm leaves and forming a basal rosette]

Capillare: Answers to key questions leading to this species (in genus Panicum). 
Plants annual, lacking rhizomes; culms usually +/- strongly branching from lower nodes; culm nodes pilose or puberulent; leaf sheaths densely to sparsely pilose; NOT [Plants perennial, rhizomatous with scaly, creeping rhizomes, often forming a knotty crown; culms unbranched at lower nodes and rarely branched above; culm nodes glabrous; leaf sheaths glabrous except for the throat, collar and distal margins]
Spikelets < 4 mm long; panicles erect, not nodding at maturity, open and very diffuse, often over 1/2 the plant length, detaching as a whole to tumble for seed dispersal; NOT [Spikelets >= 4 mm long; panicles often arching or nodding at maturity, usually compact, less than 1/2 as long as wide, much less than 1/2 the plant's total length, not detaching as a whole unit to become tumbleweeds]