Digitaria, sensu Clayton & Renvoize, 1986

Sánchez-Ken, J. Gabriel, 2017, Digitaria clarkiae (Paniceae, Panicoideae, Poaceae), a new species with a paniculate synflorescence, and the first record of D. costaricensis from México, Phytotaxa 321 (1), pp. 125-138 : 134-135

Key to the species of Digitaria in México.

1. Spikelets in groups of three or more at least in the middle of the primary branch............................................................................2

- Spikelets paired or solitary...............................................................................................................................................................15

2. Sterile lemma and second glume glabrous.........................................................................................................................................3

- Sterile lemma and second glume pilose, or at least one of them with some hairs on the apex or margins....................................... 4

3. Plants annual; spikelets 1.6–2 mm long ............................................................................................................................................... .................................. D. filiformis ( Linnaeus 1753: 57) Koeler (1802: 26) var. laeviglumis ( Fernald 1920: 102) Wipff (1996: 348)

- Plants perennial; spikelets 2.3–2.4 mm long........................................................... D. bakeri ( Nash 1898: 296) Fernald (1920: 102)

4. Hairs of the spikelet bracts brown......................................................................................................................................................5

- Hairs of the spikelet bracts white or yellowish..................................................................................................................................6

5. Spikelets 2.3–2.6 mm long, 1–1.1 mm wide; first glume glabrous; sterile lemma 7-veined; anthers 1–1.1 mm long........................ .............................................................................................................. D. badia ( Scribner & Merrill 1901: 12) Fernald (1920: 104)

- Spikelets 2.6–2.7 mm long, 1.3–1.4 mm wide; first glume pilose; sterile lemma 5-veined; anthers 1.3–1.4 mm long ...................... ..................................................................................................................................... D. michoacanensis Sánchez-Ken (2012: 129)

6. Primary branch rachis winged; spikelet bracts hairs with verrucose walls........................................ D. violascens Link (1827: 229)

- Primary branch rachis triquetrous; spikelet bracts hairs with smooth walls......................................................................................7

7. Sterile lemma with two types of hairs, the first type yellow to gold, glassy, setaceous with an acute apex, up to 0.8 mm long, mixed with a second type which are shorter, whitish and more delicate with bulbous apex .......................................................................... ................................................................................................... D. argillacea ( Hitchcock & Chase 1917: 296) Fernald (1920: 104)

- Sterile lemma with one type of hairs with bulbous apex....................................................................................................................8

8. Second glume and sterile lemma 7-veined........................................................ D. paniculata Soderstrom ex McVaugh (1983: 143)

- Second glume 0–3-veined; sterile lemma 5–7-veined........................................................................................................................9

9. Second glume up to 0.5 mm long, less than half the length of the spikelet, 0-veined.....................................................................10

- Second glume 0.5–0.8 mm long, more than half the length of the spikelets, if less, then 3-veined................................................11

10. Spikelets 1.3–1.5 mm long; plants annual; anthers ca. 0.5 mm long ............................... D. breedlovei Pohl & Davidse (1992: 106)

- Spikelets 1.8–2.7 mm long; plants perennial; anthers 1.3–1.5 mm long.................................... D. curtigluma Hitchcock (1927: 84)

11. Second glume half the length of the spikelets, with some hairs toward the apex; plants perennial; sterile lemma 7-veined.............. ............................................................................................................................................................................................... D. bakeri

- Second glume more than half the length to as long as the spikelets, pilose; plants annual or perennial; sterile lemma 5–7-veined...........................................................................................................................................................................................................12

12. Fertile lemma 1.4–1.9 mm long; anthers 0.3–0.5 mm long; plants annual .......................................................................................... .................................................................................................... D. filiformis ( Linnaeus 1753: 57) Koeler (1802: 26) var. filiformis

- Fertile lemma 1.9–2.5 mm long; anthers 0.8-1.1 mm long; plants annual or perennial.......................................................................

13. Plants annual; spikelets elliptic, with base and apex rounded............................... D. ternata ( Richard 1851: 405) Stapf (1898: 376)

- Plants perennial; spikelets ovate-lanceolate, with base and apex narrowed to attenuate.................................................................14

14. Ligule 0.6–0.8 mm long; blades up to 9(–13) cm long; plants geniculate at the base ....................... D. obtusa Swallen (1953: 425)

- Ligule 1.3–2.6 mm long; blades 15–25 cm long; plants erect.............................. D. leucocoma ( Nash 1898: 295) Urban (1920: 24)

15. Spikelets with very long pedicels forming an open paniculate synflorescence, primary branches verticillate, subverticillate or along the main axis.....................................................................................................................................................................................16

- Spikelets with very short pedicels, apparently forming racemose branches, primary branches digitate, verticillate or along the main axis....................................................................................................................................................................................................18

16. Sterile lemma veins unequally spaced, spaces between the central veins glabrous; plants annual or short-lived perennials ............. ............................................................................................................................................................................................ D. clarkiae

- Sterile lemma veins equally spaced, spaces between all veins pilose; plants perennial with knotty bases.....................................17

17. Spikelets 2.3–3.3 mm long; second glume 3-veined........................................................................................................ D. pubiflora

- Spikelets 3.5–4.6 mm long; second glume 5–7-veined................................................................................................... D. arenicola

18. Spikelets of the pair dimorphic.................................................... D. bicornis ( Lamarck 1791: 176) Roemer & Schultes (1817: 470)

- Spikelets of the pair homomorphic...................................................................................................................................................19

19. Sterile lemma veins equally spaced..................................................................................................................................................20

- Sterile lemma central veins evidently distant to each other, leaving spaces wider than the spaces between the lateral veins........23

20. First glume a minute rim less than 0.3 mm long or wanting, truncate; spikelets 1.5–4 mm long; sterile lemma 7–9-veined.........21

- First glume triangular or ovate, 0.3–1 mm long; spikelets 2.5–5 mm long; sterile lemma 5-veined...............................................22

21. Spikelets 1.5–2 mm long; second glume 3-veined; synflorescence lower primary branches commonly rebranched ......................... ......................................................................................................... D. velutina ( Forsskal 1775: 17) Palisot de Beauvois (1812: 51)

- Spikelets 3.5–4 mm long; second glume 5–7-veined; synflorescence lower primary branches not rebranched ....... D. costaricensis

22. Spikelets 4–5 mm long; sterile lemma central veins spaces glabrous, the lateral spaces pilose; sterile lemma hairs up to 2 mm long, usually yellow, sometimes whitish ............................................................... D. sellowii ( Müller Hal 1861: 315) Henrard (1934: 99)

- Spikelets 2.5–3.1 mm long; sterile lemma veins spaces all pilose; sterile lemma hairs up to 1 mm long, white to purple................. ....................................................................................................................... D. hitchcockii ( Chase 1911: 110) Stuckert (1914: 287)

23. Sterile lemma central or lateral veins scabrous or scabrellous.........................................................................................................24

- Sterile lemma with veins glabrous...................................................................................................................................................26

24. Sterile lemma glabrous between veins; central veins glabrous, only the lateral veins scabrellous above the middle; plants annual. ...................................................................................................................... D. sanguinalis ( Linnaeus 1753: 57) Scopoli (1771: 52)

- Sterile lemma pilose between the lateral veins; central veins scabrous or scabrellous from the base to the apex or only above the middle, sometimes just a few prickles toward the apex seen with high magnification; plants perennial........................................25

25. Ligule eciliate; primary branches verticillate or along the axis ......................... D. milanjiana ( Rendle 1894: 56) Stapf (1919: 430)

- Ligule ciliolate; primary branches verticillate on a short axis ......................................................... D. eriantha Steudel (1829: 468)

26. Sterile lemma hairs 1.5–6 mm long..................................................................................................................................................27

- Sterile lemma hairs up to 1 mm long................................................................................................................................................29

27. Sterile lemma central and lateral veins spaces all pilose, hairs silky, yellow to whitish...................................................................... .................................................................................. D. insularis ( Linnaeus 1759: 1304) Fedde in Schumann & Fedde (1904: 778)

- Sterile lemma central veins spaces glabrous, the lateral spaces to the central veins pilose, hairs silky, white to purplish..............28

28. Fertile lemma elliptic-lanceolate, slightly plump; sterile lemma 5-veined .......................................................................... D. patens

- Fertile lemma ovate-lanceolate, slightly flattened; sterile lemma 5–7-veined..................................................................................... ...................................................................................................................... D. californica ( Bentham 1844: 55) Henrard (1934: 99)

29. Sterile lemma glabrous or with sparse and minute hairs at the margins .............................................................................................. ................................................................................................. D. abyssinica (Hochst. ex A. Richard 1851: 360) Stapf (1907: 213)

- Sterile lemma veins spaces pilose toward the sides and margins.....................................................................................................30

30. Second glume nearly as long as the spikelet....................................................................................................................................31

- Second glume up to one third as long as the spikelet.......................................................................................................................32

31. Sterile lemma hairs 0.5–0.6 mm long.................................................................................................................................. D. leucites

- Sterile lemma hairs 0.1–0.3 mm long................................................................................................................................... D. texana

32. Rachis of the primary branches with a few long hairs, usually in the lower half ................... D. horizontalis Willdenow (1809: 92)

- Rachis of the primary branches without long hairs..........................................................................................................................33

33. First glume triangular to ovate, 0.2–0.8 mm long; sterile lemma hairs 0.5–1 mm long; second glume (1.2–) 1.5–2.7 mm long........ ............................................................................................................................................................................................. D. ciliaris

- First glume wanting or a truncate rim up to 0.1 mm long; sterile lemma hairs 0.1–0.2 mm long; second glume 0.5–1.3 mm long .. ........................................................................................................................... D. setigera Roth in Roemer & Schultes (1817: 474)