Alyssum L.

50. Alyssum L. 1

Annual to perennial herbs; hairs branched or stellate, rarely mixed with unbranched hairs; rarely the indumentum lepidote. Sepals erecto-patent, not saccate at base; petals yellow, entire to shallowly bifid; filaments of the long stamens usually winged, of the short stamens usually with an appendage. Fruit a latiseptate silicula; valves without a conspicuous median vein; style distinct but often short; stigma capitate or emarginate. Seeds 1—2(—6) in each loculus, often winged or margined.

The indumentum is said to be dimorphic when it is composed of appressed stellate hairs mixed with long, patent, unbranched or branched hairs or with stellate hairs with some long, patent rays. The measurements given for the diameter of the stellate hairs are for the usually peltate tops of these hairs. Basal leaves are those at the bottom of non-flowering rosettes or stems.

Most species occur in dry, rocky, stony, or sandy places or on cliffs, although species 6-16 often occur as weeds.

A taxonomically difficult genus in which the status and circumscription of many of the taxa differ widely in previously published treatments. This is particularly true in the perennial species of Sect. Alyssum and in Sect. Odontarrhena .

Literature: J. Baumgartner, Jahresb. Landes-Lehrersem. Wiener-Neustadt 34: 1-35 (1907): 35: 1-58 (1908); 36: 1-38 (1909) (Sect. Alyssum ). J. Baumgartner, Jahresb. LandesLehrersem. Baden bei Wien 48: 1-18 (1911) (Sect. Alyssum ). E. I. Nyârâdy. Bui. Gràd. Bot. Cluj 7: 1-51, 65-160 (1927), 8: 152-156 (1928), 9: 1-68 (1929) (Sect. Odontarrhena ). E. I. Nyârâdy, Anal. Acad. Romàne (Sect. Geol., Geogr., Biol.) ser. A, 1 (3): 1-133 (1949) (Sect. Odontarrhena ).1234567891011 1 Ovules and seeds 4 or more in each loculus

2 Annual; lower leaves linear; style 0-3-0-6 mm 5. linifolium

2 Perennial; lower leaves oblong-oblanceolate to obovate; style

1-2 mm

3 Sepals not more than 2-5 mm; silicula (3-5—)4-5—5-5 mm

1. corymbosum

3 Sepals 3-3-5 mm; silicula 7-10 mm 2. leucadeum

1 Ovules and seeds 1-2 in each loculus

4 Ovules and seeds usually solitary in each loculus (sect. Odon­ tarrhena)

5 Leaves bicolorous, green or grey-green on the upper surface,

grey or white beneath

6 Silicula very densely pubescent, the hairs completely covering the valves

7 Style 1-5-3 mm in fruit, glabrous (Krym) 60. longistylum

7 Style not more than 1-5(—2) mm in fruit, usually pubescent

8 Petals 3-5-4 mm; hairs on the silicula c. 0-5 mm in diameter 44. argenteum

8 Petals 2-3 mm; hairs on the silicula c. 0-3 mm in diameter

9 Leaves of the non-flowering stems flat 59. tortuosum

9 Leaves of the non-flowering stems plicate 62. serpyllifolium

6 Silicula glabrous or pubescent, the valves visible beneath

the hairs

10 Silicula acute or subacute

11 Basal leaves 7-11 (-15) x 4-7 mm, broadly obovate; plant with numerous non-flowering rosettes

49. smolikanum

11 Basal leaves not more than 3-4 mm wide, spathulate or obovate-spathulate; plant with long non-flowering stems 12 Seeds not winged; style of silicula 1-5-3 mm

60. longistylum 12 Seeds winged; style of silicula not more than 2 mm

13 Basal and cauline leaves similar, obovate-spathulate; silicula ± densely pubescent 48. robertianum 13 Basal and cauline leaves dissimilar, the basal spathulate, the cauline oblanceolate, larger than the basal; silicula glabrous or sparsely pubescent

50. bertolonii 10 Silicula obtuse, truncate or emarginate

14 Petals 3-3-5 mm; sepals 2-2-5 mm

15 Petals entire; silicula glabrous or sparsely pubescent

50. bertolonii 15 Petals retuse; silicula pubescent 42. murale 14 Petals 2-3 mm; sepals 1-5-2 mm

16 Filaments with a multi-dentate appendage; septum of the silicula frequently asymmetrical in outline

45. fallacinum 16 Filaments with an entire or 1- to 2-dentate appendage; septum of the silicula symmetrical in outline

17 Valves of the silicula asymmetrically inflated

18 Ovary glabrous; silicula glabrous, orbicular to suborbicular; hairs on stem 1-3 mm in diameter

51. markgrafii 18 Ovary pubescent; silicula elliptical or obovate, rarely glabrescent; hairs on stem less than 1 mm in diameter 52. corymbosoides 17 Valves of the silicula flat or symmetrically inflated

19 Leaves broadly spathulate or obovate-spathulate; valves of silicula not undulate 43. tenium 19 Leaves linear-oblanceolate to obovate-spathulate; valves of silicula usually undulate

20 Branches of the inflorescence distant, very unequal;

pedicels ± straight, rigid 42. murale 20 Branches of the inflorescence subumbellate;

pedicels strongly curved, flexuous

21 Silicula 4-6 x 3-5-4-5 mm, sparsely pubescent or glabrescent; leaves of non-flowering stems linear-oblanceolate 47. heldreichii 21 Silicula smaller, pubescent; leaves of non-flowering stems obovate-spathulate to oblanceolatespathulate 42. murale 5 Leaves concolorous, but the cauline sometimes differing from the basal in colour

22 Silicula glabrous or glabrescent

23 Petals 2-5-3 mm; basal leaves orbicular-spathulate

46. corsicum 23 Petals 3-3-5 mm; basal leaves spathulate or oblanceolate

50. bertolonii 22 Silicula pubescent

24 Hairs on the leaves at least 0-5 mm in diameter

25 Seeds winged; leaves all oblanceolate, the cauline ± decreasing in size towards the apex of the stem

55. caiiacrae 25 Seeds not winged; cauline and basal leaves usually conspicuously different in shape, the cauline ± increasing in size towards the apex of the stem

26 Stellate hairs on silicula O-A-O-7 mm in diameter; stellate hairs on leaves of non-flowering stems with unequal rays up to 1-5 mm long 54. sibiricum 26 Stellate hairs on silicula 0-2-0-4 mm in diameter; stellate hairs on leaves of non-flowering stems with equal rays not more than 0-5 mm long 56. borzaeanum 24 Hairs on leaves not more than 0-4 mm in diameter

27 Silicula 2-2-5 mm wide

28 Plant 6—35(—60) cm, decumbent; largest cauline leaves 9-25 x 2-5 mm (E. & S.E. Europe)

59. tortuosum 28 Plant 1-3 cm, procumbent; largest cauline leaves 3-

4 x 1-5 mm (Kriti) 64. fragillimum 27 Silicula 2-5 mm or more wide

29 Silicula sparsely pubescent, the valves easily visible beneath the hairs

30 Cauline leaves shorter than basal; racemes simple

(Evvoia) 53. euboeum 30 Cauline leaves longer than basal; racemes compound

31 Seeds winged; silicula 4-6 mm 50. bertolonii 31 Seeds not winged; silicula 2-3-3 -6 mm 57. obtusifolium 29 Silicula very densely pubescent, the valves completely covered by the hairs

32 Petals 3—3-5 mm; sepals 2-2-5 mm

33 Flowering stems ±erect or ascending; basal leaves

6-8 x c. 3 mm, obovate-spathulate to suborbicular;

petiole of cauline leaves 3-5 mm (U.S. S. R.)

58. obovatum 33 Flowering stems usually procumbent; basal leaves

4-8 x 1 - 5-3- 5 mm, oblanceolate to obovatespathulate; petiole of cauline leaves not more than

2 mm (Alps) 61. alpestre 32 Petals 2-3 mm; sepals usually not more than 2 mm

34 Largest cauline leaves near the apex of the stem and distinctly larger than the basal 63. nebrodense 34 Largest cauline leaves near the base of the stem,

smaller than or about equalling the basal

35 Leaves of non-flowering stems flat; hairs on the silicula 20- to 25-rayed (U.S.S. R.) 58. obovatum 35 Leaves on non-flowering stems plicate; hairs on the silicula mostly 12- to 16-rayed (S.W. Europe)

62. serpyllifolium 4 Ovules and seeds 2 in each loculus

36 Sepals with a tuft of long, divergent-rayed, stellate hairs at the apex

37 Fruitingraceme± elongate;shortstamenswitha long

(1 - 5-2 mm) appendage; style c. 4 mm 39. doerfleri 37 Fruiting racemes corymbose; short stamens with a small appendage at the base; style not more than 3 mm

40. taygeteum 36 Sepalswithouta tuftofhairsattheapex

38 Silicula glabrous or glabrescent

39 Indumentum of leaves lepidote 37. idaeum 39 Indumentum of leaves consisting of branched or stellate hairs

40 Inflorescence corymbose or paniculate, each branch terminated by a raceme

41 Valves of silicula strongly inflated; wing of seeds

0- 1 (-0- 3) mm wide 3. petraeum 41 Valves of silicula ± flat, or inflated with flat margin;

wing of seeds 0-3—1 mm wide 4. saxatile 40 Inflorescence a ± simple raceme

42 Style 1 - 5-3-5 mm

43 Petals 3 -5-4 mm; annual; leaves oblong-spathulate

11. smyrnaeum 43 Petals 6-7 mm; perennial; leaves linear-oblong or linear-lanceolate, acute 19. lenense 42 Style not more than 1 (— 1-5) mm

44 Upper leaves forming an involucre around the inflorescence; silicula ovate, the valves inflated; petals

3-3- 5 mm 10. foliosum 44 Upper leaves not forming an involucre; silicula

± orbicular, the valves inflated in the middle, with strongly flattened margin; petals 2-3 mm

45 Stellate hairs 0-2-0-3 mm in diameter; sepals deciduous 9. desertorum 45 Stellate hairs (0-4-)0-5-0-8(-l) mm in diameter; sepals persistent 12. minutum 38 Silicula pubescent

46 Indumentum of the inflorescence or the silicula consisting of long patent hairs, often mixed with appressed stellate hairs

47 Anthers less than 0- 5 mm; annual

48 Filaments without appendages; indumentum dimorphic only on the silicula 8. granatense 48 Filaments winged or with appendages; indumentum

± dimorphic on all parts of the plant

49 Petals attenuate towards the base; style 0-7-1 -3 mm

15. strigosum 49 Petals constricted at the middle; style 1 -2-2-5 mm

16. hirsutum 47 Anthers more than 0- 5 mm; biennial or perennial

50 Erect biennial up to 80 cm; middle cauline leaves usually at least 10 mm wide; hairs 5- to 7-rayed, sparse 24. wierzbickii 50 Perennial up to 40(-60)cm; often procumbent or ascending; middle cauline leaves usually less than

10 mm wide, the hairs 8- to many-rayed

51 Silicula 6 mm or more, the valves strongly inflated, without a flattened margin; racemes very short and crowded in fruit 36. lassiticum 51 Silicula up to 6(-6- 5) mm, the valves with a flattened margin; racemes very long in fruit

52 Petals entire; filaments of the long stamens entire; densely caespitose or pulvinate (Bulgaria and Romania) 26. pulvinare 52 Petals ± emarginate; filaments of the long stamens usually with 1 -2 teeth; diffuse or laxly caespitose

53 Seeds 3-3- 5 mm; sepals ±persistent (Krym)

25. calycocarpum 53 Seeds 1 - 5-2 mm; sepals deciduous

54 Silicula suborbicular to obovate; leaves on the non-flowering stems obovate-spathulate

18. repens 54 Silicula oblong-obovate or obovate; leaves on the non-flowering stems linear-oblong or linearlanceolate, acute 20. fischeranum 46 Indumentum of the inflorescence and silicula consisting of appressed hairs

55 Annual; petals2 -4(-6) mm

56 Pedicels 7-20 mm in fruit; petals 4-5-6 mm

17. rostratum 56 Pedicels not more than 5 mm; petals 2-4 mm

57 Fruiting racemes subumbellate; silicula ovate, the valves inflated 13. umbellatum 57 Fruiting racemes elongating; valves of the silicula with a flattened margin

58 Style 1 -5-1 -8 mm, dilated at base; silicula elliptical to orbicular-ovate, with dimorphic indumentum

6. dasycarpum 58 Style not more than 1 - 3 mm, slender at base; silicula

± orbicular, with monomorphic indumentum

59 Sepals persistent; style O-3-O-6 mm 7. alyssoides 59 Sepals deciduous; style 0-7- 1 -6 mm 14. minus 55 Perennial, rarely biennial; petals 5 mm or more

60 Silicula 8-9 mm; petals 7-8 mm (Olimbos) 38. handelii 60 Silicula less than 8 mm; petals usually smaller

61 Hairs on the leaves 5- to 10-rayed

62 Silicula elliptical or elliptic-orbicular, distinctly longer than wide 21. scardicum 62 Silicula ± orbicular

63 Basal leaves linear-lanceolate to oblanceolate-spathulate; cauline linear or linear-spathulate; hairs on leaves usually not more than 0- 5

(-0-7) mm in diameter 27. montanum 63 Basal leaves obovate to elliptical; cauline elliptical, cuneate; hairs on leaves 0-7-1 mm in diameter

29. diffusum 61 Hairs on leaves 10- to many-rayed

64 Lower pedicels shorter than the silicula; valves of silicula dissimilar 41. densistellatum 64 Lower pedicels equalling or longer than silicula; valves of silicula similar

65 Lower pedicels 10-15 mm in fruit, often deflexed

35. sphacioticum 65 Lower pedicels less than 10 mm in fruit, patent or erecto-patent

66 Silicula 6 mm or more, elliptical or ellipticorbicular

67 Silicula densely grey-pubescent 30. cuneifolium

67 Silicula green, sparsely pubescent

68 Petals glabrous; silicula 6-6-5 mm; basal leaves oblong-obovate, gradually attenuate into petiole 22. wulfenianum

68 Petals pubescent on the back; silicula 6-5-8 mm;

basal leaves orbicular-obovate, abruptly contracted into petiole 23. ovirense

66 Silicula not more than 6 mm, orbicular, rarely elliptic-orbicular

69 Basal leaves ± abruptly contracted into petiole

70 Hairs on the leaves c. 0-4 mm in diameter

33. moellendorfìanum

70 Hairs on the leaves 0-5-0-7 mm in diameter

71 Basal leaves suborbicular; cauline ovatespathulate 31. arenarium

71 Basal leaves broadly spathulate to obovate;

cauline oblanceolate or spathulate

72 Lower pedicels l |- 2 times as long as the silicula; silicula orbicular; non-flowering stems long 34. stribrnyi

72 Lower pedicels about equalling silicula; silicula elliptic-orbicular; non-flowering stems very short, terminated by a rosette 30. cuneifolium

69 Basal leaves gradually attenuate towards the base,

not obviously petiolate

73 Petals 6-8 mm; leaves usually white or grey

32. atlanticum

73 Petals 3-6 mm; leaves usually green or greygreen

74 Silicula 3-5-5 mm 27. montanum

74 Silicula 2-5-3 mm 28. fastigiatum