Astragalus

Castillón, Eduardo Estrada, Quintanilla, José Ángel Villarreal & Salinas, Alfonso Delgado-, 2022, A new section of Astragalus (Fabaceae: Galegeae) from Mexico, Phytotaxa 545 (1), pp. 79-86 : 83-84

Key to identify the different sections of Astragalus in Mexico.

1. Stipules always free or the lowest semi or almost fully amplexicaule, but never connate ................................................................2

- Stipules, at least at the lowest nodes connate...................................................................................................................................20

2. Plants densely pubescent with short curly trichomes mixed with longer spirally twisted ones, appressed or spreading up to 2 mm long.....................................................................................................................................................................................................3

- Plant variously pubescent, but the trichomes 1.5 mm long or shorter, none spirally twisted ............................................................4

3. Stems prostrate or decumbent, usually shorter than the longest leaves; flowers ascending; pods humistrate with age, soon caducous ..................................................................................................................................................................... sect. Mollissimi

- Stems erect, caulescent, the stems longer than longest leaves; flowers soon deflexed; pod erect, never humistrate, persistent......... ....................................................................................................................................................................................... sect. Gigantei

4. Always annual; ovary (and pod) with 2 ovules only.............................................................................................. sect. Microlobium

- Annual or perennial; ovary (and pod) with 4 or more ovules ............................................................................................................5

5. Flowers red or, if purple, the plants acaulescent ................................................................................................................................6

- Flowers purple, blue, white, lilac, concolorous, or mixtures of these colors, but never completely red; caulescent plants..............7

6. Calyx-tube shallowly campanulate, 2–4.5 mm long; banner 14 mm long or shorter; pubescence always dolabriform sect. Lotiflori

- Calyx-tube cylindric or deeply campanulate, 6–10.5 mm long; banner 16–22 mm long; pubescence simple or dolabriform............ .................................................................................................................................................................................... sect. Argophylli

7. Pod inflated, bladder-like of papyrus texture, stiffly so or papery-membranous, unilocular or bilocular .........................................8

- Pod triquetrous or dorsoventrally flattened, not bladdery inflated, narrow elliptic, linear-oblong, oblong-elliptic, oblique-obovate or subterete in cross section, always bilocular .................................................................................................................................14

8. Flowers very small, banner 5.5–6.5 mm long; pod 4–8 mm long, persistent ................................................................sect. Scalares

- Flowers longer than 7 mm; pod much longer than 8 mm, caducous..................................................................................................9

9. Pod stipitate, the stipe 7–17 mm long ....................................................................................................................... sect. Trichopodi

- Pod sessile to subsessile, stipe (if present), 0.2-0.5 mm long ..........................................................................................................10

10. Pod unilocular...................................................................................................................................................................................11

- Pod bilocular (at least below the apex or beak .................................................................................................................................12

11. Lowest stipules semi or almost fully amplexicaule......................................................................................................sect. Densifolii

11. Stipules all free ...................................................................................................................................................................sect. Inflati

12. Banner 7–9.5 mm long; pod retuse in both extremes even when young, minutely apiculate and bilocular at apex............................ .........................................................................................................................................................................................sect. Diphaci

- Banner 10–16 mm long; pod never retuse in both extremes, the apex ending into a triangular unilocular beak ............................13

13. Pod 12–23 mm long; pedicels persistent; ovules 10–42; calyx campanulate, teeth shorter than the tube...................... sect. Diphysi

- Pod 6–8 mm long; pedicels caducous; ovules 4; calyx urceolate-suboblong to urceolate-globose, the teeth the same size as the tube ................................................................................................................................................................................ sect. Rupertii

14. Peduncles dimorphic, the early ones very short, up to 2.6 cm long, with only 1–2 flowers, the later ones, up to 7-flowered; the banner 5–5.5 mm long; pod pendulous, sessile, subunilocular, 6–10 mm long......................................................sect. Quinqueflori

- Peduncles homomorphic, if flowers are small, the root annual and pod larger, if the pod is small, the flowers more than 7-flowered; pod fully bilocular ............................................................................................................................................................................15

15. Pod declined or deflexed, sessile, or elevated on a stipe-like gynophore, the body very strongly dorsoventrally compressed, peltiform or shield-shaped, as broad as long or not much longer ................................................................................. sect. Scutanei

- Pod ascending, spreading or deflexed, sessile or stipitate, sometimes shortly so, the body mostly lance-oblong, in profile, half ovate, in any case triquetrous or compressed triquetrous, or the body subterete to dorsoventrally flattened, linear-oblong, elliptic, oblong-elliptic, ovate-elliptic to wide-elliptic to wide-oblong, twice to many times longer than wide...........................................16

16. Pod dorsoventrally flattened, somewhat bulged, persistent on the receptacle, the body elliptic, oblong-elliptic to ovate-elliptic, straight, dorsoventrally compressed, one to one and a half longer than wide...........................................................sect. Sagitticarpi

- Pod triquetrous and triangular in section or subterete, twice to many times longer than wide........................................................17

17. Pod stipitate ......................................................................................................................................................................................18

- Pod sessile ........................................................................................................................................................................................19

18. Pod pendulous ................................................................................................................................................................. sect. Miselli

- Pod incurved-ascending...................................................................................................................................... sect. Reventi-Arrecti

19. Pod deflexed; flowers very small, 4–9 mm long, early deflexed, usually very numerous (15–65) ............................ sect. Micranthi

- Pod ascending or loosely spreading; flowers either few or longer than 9 mm, ascending or loosely spreading ................................. ....................................................................................................................................................................................sect. Leptocarpi

20. Plants restricted to Baja California ...................................................................................................................................................21

- Plants throughout Mexico excluding Baja California ......................................................................................................................25

21. Petals large, banner 21–28 mm long; petals of the wings 19.5–25 mm long; keel petals 17.3–21 mm long; in Mexico, recorded only around Mexicali (BC)................................................................................................................................................... sect. Preusiani

- Petals, all shorter; plants around Mexicali and other areas of Baja California ................................................................................22

22. Pod oblong to elliptic, laterally compressed, unilocular, narrowed at both ends, basally ending in a stipe or the pod faces inflated only in the area where seeds are located ..........................................................................................................................................23

- Pod widened or inflated resembling a bladder .................................................................................................................................24

23. Pod oblong to elliptic, laterally compressed, unilocular, narrowed at both ends, basally ending in a stipe .............. sect. Cusickiani

- Pod inflated resembling a bladder, but its faces inflated only in the area where seeds are located ..............................sect. Oxyphysi

24. Plant small, the stems up to 11 cm long; peduncles 0.5–1.5 cm long; petals small, banner 7.3–10 mm long, petals of the wings 7–9.3 mm long, keel petals 6.9–8.8 mm long; mountains of Sierra de Juárez and Sierra de San Pedro Mártir; conifer forest, 1700– 2475 m ....................................................................................................................................................................... sect. Circumdati

- Plants larger, the stems 30–70 cm long; peduncles 2.5–10 cm long; petals larger; coastal dunes............................ sect. Anemophili

25. Pubescence dolabriform, the trichomes joined at a point before the end, in the form of “v” or “t”, with equal or unequal ends ....... ..........................................................................................................................................................................................................26

- Pubescence basifixed with simple trichomes ...................................................................................................................................27

26. Pod deflexed, bilocular, triquetrous, oblong to narrow–oblong; banner 6–8.2 mm long............................................ sect. Hypoleuci

- Pod ascendant, unilocular, inflated resembling a bladder, oblong–elliptic; banner 8.3–11.8 mm long ............................................... .................................................................................................................................................................................... sect. Humistrati

27. Petals all red; banner 22–32 mm long; petals of wings 18–31 mm largo; keel petals 18–27 mm long.....................sect. Sarcocarpi

27. Petals of another color, or if red, combined with another color; banner, wings, and keel of smaller size .......................................28

28. Pubescence of stems, petioles and peduncles dense, hispid to pilose, the trichomes straight extended or retrorse; petals purple; ovules 9–18; pod oblong to narrow-oblong, triquetrous, laterally compressed, glabrous .......................................... sect. Greggiani

- Pubescence of stems, and peduncles hispid to pilose or nearly glabrous, but the trichomes appressed or ascending; pod either or different form, but if the same form, then pubescent or if trichomes extended or retrorse, then the flowers yellow ......................29

29. Pod pendulous, stipitate, sometimes obscurely so............................................................................................................................30

- Pod either deflexed or ascending, always sessile .............................................................................................................................31

30. Body of the pod sharply triquetrous, unilocular; seleniferous, ill scented plants.......................................................... sect. Bisulcati

- Body of the pod mostly obcompressed, dorsally excavated, unilocular to fully bilocular, a septum always present; not of seleniferous soils, scentless plants ...................................................................................................................................................sect. Strigullosi

31. Body of the pod unilocular ......................................................................................................................................... sect. Scytocarpi

- Body of the pod semi or fully bilocular........................................................................................................................sect. Strigulosi