Home Flora of Missouri
Home
Name Search
Families
Volumes
Panicum L. Search in The Plant ListSearch in IPNISearch in Australian Plant Name IndexSearch in Index Nominum Genericorum (ING)Search in NYBG Virtual HerbariumSearch in JSTOR Plant ScienceSearch in SEINetSearch in African Plants Database at Geneva Botanical Garden Decrease font Increase font Restore font
 

Published In: Species Plantarum 1: 55. 1753. (1 May 1753) (Sp. Pl.) Name publication detailView in BotanicusView in Biodiversity Heritage Library
 

Project Name Data (Last Modified On 7/9/2009)
Acceptance : Accepted
Project Data     (Last Modified On 8/6/2009)

 

Export To PDF Export To Word

65. Panicum L. (panic grass)

Plants with C3 or C4 photosynthesis, annual or perennial, rarely with stolons, forming tufts, clumps, or rarely colonies. Flowering stems erect to ascending or rarely spreading in the basal portion and rooting at the lower nodes, glabrous or hairy, sometimes with a dense ring (beard) of downwardly pointing hairs at the nodes. Leaves often differentiated into a dense basal rosette of shorter overwintering leaves and fewer, longer leaves on the flowering stems. Leaf sheaths glabrous or hairy, the ligule a line or band of hairs or a membrane, this glabrous or more commonly with a fringe of hairs along the margin. Leaf blades usually flat, the base rounded or abruptly narrowed, glabrous or hairy. Inflorescences dense or more commonly open panicles with at least some of the branches rebranched 1 or more times (except in P. obtusum), the spikelets densely or loosely spaced along the branches, these not appearing 1‑sided (except sometimes in P. obtusum), the axis with a spikelet at the tip. Spikelets not subtended by bristles or spines, without a cuplike ring or knoblike disk at the base. Lower glume much shorter than to less commonly about as long as the rest of the spikelet, wrapped around the spikelet base, awnless, glabrous. Upper glume about as long as the rest of the spikelet, not inflated or saclike at the base, rounded to sharply pointed at the tip, awnless. Lowermost floret staminate or sterile, the lemma about as long as the rest of the spikelet, awnless. Fertile (perfect) floret with the lemma shorter than that of the staminate or sterile floret, rounded at the tip, awnless, nerveless or obscurely nerved, glabrous, shiny or dull, thickened and hard (usually somewhat bonelike) at maturity, the margins also thick, wrapped around the palea and fruit, including the tip (after flowering). Paleas glabrous, shiny or dull, thickened and hard (usually somewhat bonelike) at maturity. Fruits narrowly to broadly oblong‑elliptic in outline. About 500 species, nearly worldwide, mostly in tropical and subtropical regions.

Perhaps no question of generic limits in grasses is more controversial than whether to segregate Dichanthelium from Panicum or to treat it as a subgenus within the latter genus. There seems little doubt that the species of Dichanthelium form a natural group, which Gould (1974) first elevated to generic level. Characters used to differentiate Dichanthelium from the rest of Panicum include: a C3 (vs. mostly C4) life cycle and the associated anatomical characters; production of an overwintering rosette of basal leaves that are morphologically distinct (shorter and broader) from the leaves of the flowering stems; 2 flowering periods each year, with more prominent inflorescences from relatively unbranched flowering stems in the spring (vernal flowering) followed by the production of fascicles of short branches on these stems with smaller inflorescences (often with cleistogamous spikelets) usually partially hidden by the leaves in the autumn (autumnal flowering); anatomical differences in the growing tips of stems; and micromorphological differences in the surfaces of the paleas (see table of comparisons in Gould and Clark, 1978). In the present treatment, species 1, 3, 4, 6–8, 10, 13–17, 20, 22, 23, 25, and 26 are members of the Dichanthelium group, whereas species 2, 5, 9, 11, 12, 18, 19, 21, 24, and 27 belong to the rest of Panicum.

However, Gould and his coworkers appear to have been most familiar with North American members of the group. Subsequent analyses of South American species in the Dichanthelium group, particularly the anatomical studies of Zuloaga and his collaborators (see Zuloaga and Morrone, 1991), have shown that there exist species that are intermediate for the characters supposedly separating Dichanthelium from the rest of Panicum. Also, the group of species related to P. hians (subgenus Steinchisma (Raf.) Zuloaga) have long been known to possess anatomy and physiology somewhat intermediate between the C3 and C4 types. Recently, in a numerical study of 64 characters and 188 New World species, Zuloaga et al. (1993) found strong evidence that American Panicum in the broad sense consists of five major lineages (with a number of subgroups within each lineage), and that species of Dichanthelium are nested in a larger lineage containing species considered part of Panicum by most botanists. Thus, the more conservative approach of treating Panicum in the broad sense, including Dichanthelium, is followed provisionally in the present treatment, in agreement with many other authors (including Lelong, 1986; Webster, 1988; Crins, 1991; Gleason and Cronquist, 1991; Zuloaga et al., 1993).

Whatever the generic treatment of Panicum, most botanists currently agree that too many species were recognized by earlier authors (including Steyermark, 1963). More recent revisions of portions of the genus (Gould and Clark, 1978; Lelong, 1984, 1986; Hansen and Wunderlin, 1988) have treated numerous taxa as minor morphological variants of other species. This has resulted in lengthy lists of synonyms for some of the widespread taxa, as well as relatively numerous varieties accepted for some of these species. A few of the species complexes, particularly those centered on P. acuminatum and P. dichotomum, are in need of more detailed biosystematic studies. Ecologists and field biologists sometimes have argued that various entities placed in synonymy under common, widespread species occupy discrete ecological niches and deserve taxonomic recognition at some level. It is difficult without more detailed taxonomic study to evaluate whether such cases are based upon genuinely distinct biological entities or merely reflect morphological variability within a small part of the range of a widespread species.

 

Export To PDF Export To Word Export To SDD
Switch to indented key format
1 1. Plants producing long (to 3 m), vinelike stolons at the base in addition to the erect or ascending flowering stems; inflorescences with the primary branches erect or strongly ascending spikelike racemes, usually not rebranched; lower glume more than 3/4 as long as the rest of the spikelet...20. P. OBTUSUM

Panicum obtusum
2 1. Plants not producing distinct stolons; inflorescences with the primary branches ascending to spreading (except sometimes in P. linearifolium), not spikelike, at least the lowermost branches rebranched 1 or more times; lower glume often less than 3/4 as long as the rest of the spikelet

3 2. Basal leaves and those of the flowering stems similar in size and shape

4 3. Leaves mostly erect, crowded toward the base of the plant (due to the very much shortened internodes toward the bases of the flowering stems), the leaves above the bases of the flowering stems few or none

5 4. Spikelets 2.9–4.5 mm long, the upper glume and lemma of the sterile floret extended past the fertile floret into a sharply pointed, noticeable beak...8. P. DEPAUPERATUM

Panicum depauperatum
6 4. Spikelets 1.7–3.2 mm long, the upper glume and lemma of the sterile floret about as long as the fertile floret and rounded to bluntly pointed, not forming a beak

7 5. Leaf blades light green to yellowish green, (3–)5–12 mm wide, mostly 10–15 times as long as wide, relatively thin and soft; ligule a minute membrane 0.2–0.5 mm long, this glabrous or sometimes minutely hairy on the margin...14. P. LAXIFLORUM

Panicum laxiflorum
8 5. Leaf blades bright green to bluish green, 1–5 mm wide, mostly more than 20 times as long as wide, relatively thick and firm; ligule a line or band of hairs 0.5–1.0 mm long...16. P. LINEARIFOLIUM

Panicum linearifolium
9 3. Leaves basal and scattered along most of the length of the flowering stems, not mostly crowded near the base

10 6. Leaf sheaths glabrous, except sometimes at the tip or along the upper margins; flowering stems with the nodes glabrous

11 7. Upper glume and lemma of lower floret with abundant small blisterlike warts or tubercles, otherwise glabrous...27. P. VERRUCOSUM

Panicum verrucosum
12 7. Spikelets with the glumes and lemmas not appearing warty or with small tubercles, glabrous or hairy

13 8. Lower glume less than 1/3 as long as the rest of the spikelet, rounded or bluntly pointed at the tip; plants annual, with a relatively soft base, forming tufts...9. P. DICHOTOMIFLORUM

Panicum dichotomiflorum
14 8. Lower glume 1/3 to about as long as the rest of the spikelet, sharply pointed at the tip; plants perennial, with rhizomes or hard, knotty bases, forming clumps or dense tufts

15 9. Leaf sheaths with the ligule a band of hairs 2–4 mm long; inflorescences with the ultimate branches not appearing 1-sided, the spikelets (3.7–)4.0–6.0 mm long, oriented in several directions...28. P. VIRGATUM

Panicum virgatum
16 9. Leaf sheaths with the ligule a short membrane 0.3–1.0 mm long; inflorescences with the ultimate branches appearing somewhat 1-sided, the spikelets 1.7–3.9 mm long, oriented more or less in 2 rows

17 10. Flowering stems 1–2 mm in diameter below the middle, slender, wiry; sterile floret with the palea inflated and hardened at maturity, distorting the spikelet...12. P. HIANS

18 10. Flowering stems 3–6 mm in diameter below the middle, relatively stout and stiff; sterile floret with the palea not inflated or hardened at maturity, mostly hidden by the lemma

19 11. Plants with long-creeping rhizomes; only the basal portions of flowering stems and lowermost leaf sheaths somewhat flattened and keeled; spikelets obliquely curved or turned at an angle from their short stalks...2. P. ANCEPS

Panicum anceps
20 11. Plants with hard, knotty bases, but lacking rhizomes; flowering stems and leaf sheaths somewhat flattened and keeled their entire length; spikelets not curved or angled with respect to their short stalks...24. P. RIGIDULUM

Panicum rigidulum
21 6. Leaf sheaths hairy; flowering stems with at least the lowermost nodes usually hairy

22 12. Plants perennial, with long-creeping rhizomes, forming clumps; inflorescences with the ultimate branches appearing somewhat 1-sided, the spikelets oriented more or less in 2 rows, obliquely curved or turned at an angle from their short stalks...2. P. ANCEPS

Panicum anceps var. anceps
23 12. Plants annual, without rhizomes, forming tufts; inflorescences with the ultimate branches not appearing 1-sided, the spikelets oriented in several directions, not curved or angled with respect to their short stalks

24 13. Spikelets 4.5–6.0 mm long; inflorescences usually somewhat arched or nodding...18. P. MILIACEUM

Panicum miliaceum
25 13. Spikelets 1.5–3.6 mm long; inflorescences erect to spreading, but with the main axis straight and not arched or nodding

26 14. Inflorescences 2–3 times as long as wide...11. P. FLEXILE

Panicum flexile
27 14. Inflorescences less than 2 times as long as wide, often about as long as wide

28 15. Fruits 1.4–2.0 mm long, narrowly elliptic to elliptic in outline; fertile lemma light yellow or straw-colored at maturity; spikelets tapered to a relatively long, narrow, sharp point at the tip; inflorescence usually more than 1/2 as long as the entire flowering stem, often breaking off at the base and becoming a “tumbleweed” at maturity...5. P. CAPILLARE

Panicum capillare
29 15. Fruits 1.2–1.5 mm long, broadly elliptic in outline; fertile lemma tending to darken or turn blackish at maturity; spikelets narrowed or tapered to a short, sharp point at the tip; inflorescence up to 1/3 as long as the entire flowering stem, remaining attached to the flowering stem at maturity, not becoming a “tumbleweed”...21. P. PHILADELPHICUM

Panicum philadelphicum
30 2. Basal leaves noticeably shorter and often also broader than those of the flowering stems

31 16. Ligules conspicuous, some or all with the hairs 2–5 mm long

32 17. Spikelets 1.2–2.2 mm long...1. P. ACUMINATUM

Panicum acuminatum
33 17. Spikelets 2.7–4.3 mm long

34 18. Nodes of the stems glabrous or with short, ascending to spreading hairs...20. P. OLIGOSANTHES

Panicum oligosanthes
35 18. Nodes of the stems densely bearded with long, spreading to downwardly pointed hairs...23. P. RAVENELII

Panicum ravenelii
36 16. Ligules inconspicuous or less commonly absent, the hairs less than 2 mm long

37 19. Flowering stems with a well-differentiated, broad, glabrous or glandular band below each node, elsewhere pubescent with soft, gray, velvety hairs; leaf sheaths pubescent with soft, gray, velvety hairs, usually somewhat sticky-glandular along the middle of the back...25. P. SCOPARIUM

38 19. Flowering stems without a well-differentiated, glabrous or glandular band below each node, glabrous or variously hairy; leaf sheaths glabrous or variously hairy, not sticky-glandular

39 20. Nodes of the flowering stems with a conspicuous beard of spreading or downward-pointing hairs, these longer, denser, and/or oriented in a different direction than any pubescence present on the internodes

40 21. Spikelets 3.7–5.2 mm long; leaves of the main flowering stems with the blades (9–)14–33 mm wide...4. P. BOSCII

Panicum boscii
41 21. Spikelets 1.5–3.2 mm long; leaves of the main flowering stems with the blades mostly 3–14 mm wide

42 22. Leaves mostly crowded near the base of the plant, the blades light green to yellowish green, relatively thin and soft, usually with long hairs along the margins and surfaces...14. P. LAXIFLORUM

Panicum laxiflorum
43 22. Leaves basal and also well distributed along the flowering stems, the blades dull green to dark green, relatively thick and stiff, glabrous or with short to long hairs only along the basal portions of the margins, the surfaces variously glabrous or hairy

44 23. Flowering stems and leaf blades densely pubescent with soft, velvety hairs; inflorescences with the branches pubescent with conspicuous, spreading hairs...17. P. MALACOPHYLLUM

Panicum malacophyllum
45 23. Flowering stems and leaf blades glabrous or the stems sparsely to moderately pubescent with short, stiff hairs (sometimes with a beard of longer hairs at the nodes); inflorescences with the branches glabrous or rarely sparsely pubescent with inconspicuous, short hairs

46 24. Leaf blades, especially of the lower stem leaves, heart-shaped to abruptly rounded and somewhat clasping at the base; uppermost leaf with the blade erect or strongly ascending...3. P. BOREALE

Panicum boreale
47 24. Leaf blades narrowed at the base, not clasping; uppermost leaf with the blade loosely ascending to spreading or somewhat reflexed...10. P. DICHOTOMUM

Panicum dichotomum
48 20. Nodes of the flowering stems glabrous or hairy, if pubescent then the hairs appressed, matted, or ascending, shorter than to about as long as the hairs on the internodes

49 25. Leaf sheaths all or at least those toward the base of the plant noticeably hairy on the surface, the hairs sometimes mostly worn away with age, but leaving small pustular bases

50 26. Spikelets 1.2–2.0 mm long; pubescence of at least the lowermost leaf sheaths usually of two types, with numerous, shorter, stiff, appressed hairs mixed with sparse, longer, softer, spreading hairs...22. P. PORTORICENSE

Panicum portoricense
51 26. Spikelets 2.4–4.0 mm long; pubescence of various types of hairs, but relatively uniform, with only 1 type of hair on the sheaths

52 27. Ligule 1.0–1.9 mm long, consisting of a line or band of hairs...20. P. OLIGOSANTHES

Panicum oligosanthes
53 27. Ligule 0.2–0.9 mm long or less commonly absent, if present, consisting of a very short line or band of hairs or a short, uneven membrane with minute hairs along the margin

54 28. Principal leaf blades mostly 10–28 cm long and 12–35 mm wide, the midvein and main lateral veins prominent and raised...6. P. CLANDESTINUM

Panicum clandestinum
55 28. Principal leaf blades 5–12 cm long and 5–15(–18) mm wide, the main veins about the same size and not noticeably raised from the surface

56 29. Leaf blades, especially of the lower stem leaves, heart-shaped to abruptly rounded and somewhat clasping at the base, glabrous except for the sparse hairs along the margins at the base...7. P. COMMUTATUM

Panicum commutatum
57 29. Leaf blades broadly rounded at the base, not clasping the stems, hairy on both surfaces, sometimes sparsely so on the upper surface...15. P. LEIBERGII

Panicum leibergii
58 25. Leaf sheaths all or nearly all glabrous on the surface (may be hairy along the margins), the lowermost sheaths sometimes sparsely and inconspicuously hairy when worn off, these not leaving pustular bases

59 30. Spikelets 3.2–3.8 mm long; leaf blades with the midvein and main lateral veins prominent and raised...13. P. LATIFOLIUM

Panicum latifolium
60 30. Spikelets 1.5–3.2 mm long; leaf blades with the main veins all similar or with the midvein slightly more prominent than the other veins, but not raised

61 31. Spikelets 1.3–1.9 mm long, nearly circular in outline...26. P. SPHAEROCARPUM

Panicum sphaerocarpum
62 31. Spikelets (1.5–)1.9–3.2 mm long, elliptic to obovate in outline

63 32. Leaf blades relatively soft, narrowed to broadly rounded at the base, not clasping the stems

64 33. Principal leaf blades erect or ascending; plants producing relatively few fascicles of leaves in the fall, these leaves not significantly narrower than those of the main stems, the plants not appearing bushy and the main stems remaining upright...3. P. BOREALE

Panicum boreale
65 33. Principal leaf blades more or less spreading; plants usually producing numerous fascicles of narrow leaves on short branches in the fall, appearing bushy and with the main stems often becoming top-heavy and leaning or spreading...10. P. DICHOTOMUM

Panicum dichotomum
66 32. Leaf blades relatively firm, heart-shaped to abruptly rounded and somewhat clasping at the base

67 34. Principal leaf blades erect or ascending, broadest at or near the middle...3. P. BOREALE

Panicum boreale
68 34. Principal leaf blades more or less spreading, broadest near the base...7. P. COMMUTATUM Panicum commutatum
 
 
© 2014 Missouri Botanical Garden - 4344 Shaw Boulevard - Saint Louis, Missouri 63110