Draba L.

59. Draba L. 3

Annual to perennial herbs. Leaves simple, entire or dentate. Sepals erecto-patent, the inner not or only slightly saccate at base; petals white or yellow, entire or emarginate; filaments not or only slightly dilated at the base. Fruit a latiseptate silicula or siliqua; valves more or less flat, with a median vein in the lower half; style absent to long; stigma capitate. Seeds in 2 rows in each loculus, not winged.

Most of the species are arctic or montane plants, growing in open, rocky or gravelly places. Several are common as rock-plants in gardens.

The nature and density of the indumentum is used a great deal in the taxonomy of Draba . The hairs may be unbranched, branched, stellate or medifixed. The leaves are nearly always ciliate even when they are otherwise glabrous. The length of the stem given in the description refers to the fruiting stage; there is often considerable elongation after flowering.

The limits and particularly the rank of many described taxa are disputable, and experimental work is needed in the genus.

Literature: O. E.Schulz in Engler, Pflanzenreich 89 (IV. 105): 1 -396 (1927). 1 Scapose perennials with yellow flowers 2 Plant with numerous long, procumbent leafy stems; hairs on leaves and base of stem medifixed 25. sibirica 2 Plantwithoutlong,procumbentleafy stems,oftendensely caespitose; hairs not medifixed 3 Leaves lanceolate to obovate, not keeled, soft in texture, without stiff cilia 4 Leaves with unbranched hairs only 42. crassifolia 4 Leaves with some branched and stellate hairs (18-24). alpina group 3 Leaveslinearormore rarely lanceolate,keeled, ± rigid,with stiff cilia 5 Scape hairy 6 Petals about equalling stamens 7 Scape villous, with some long hairs up to 1 mm 5. cuspidata 7 Scape hispid, with hairs not more than 0- 5 mm 3. aspera 6 Petals distinctly longer than stamens 8 Silicula densely stellately hairy 14. eretica 8 Silicula with unbranched or branched hairs only 9 Scape villous with hairs c. 1 mm 10 Style 1 -1-5 mm 12. parnassica 10 Style 0-3-0- 8 mm 15. dedeana 9 Scape hispid with shorter hairs, mostly not more than 0-75 mm 11 Style 2-4 mm; silicula ±inflated at base 11. hispanica 11 Style c. 1 mm; silicula flat 13. loiseleurii 5 Scape glabrous 12 Style not more than 1 mm in fruit 13 Plant laxly caespitose, with ± elongated stems clothed with scale-like leaf-remains below the rosette 16. sauteri 13 Plant densely caespitose or pulvinate, without obvious persistent scale-like leaf-remains 14 lnfructescence ± elongate 15 Leaves less than 1 mm wide, incurved; silicula 3 -5- 5 mm, inflated 17. heterocoma 15 Leaves 1 -2 mm wide, straight; silicula 6-9 mm, flat 9. lacaitae 14 lnfructescence subcapitate 16 Silicula obviously hairy 8. compacta 16 Silicula subglabrous 2. hoppeana 12 Style more than 1 mm (and usually more than 1 -5 mm) in fruit 17 Style less than 3 mm in fruit 18 Leaves (1- 5—) 1 -75-4 mm wide 7. lasiocarpa 18 Leaves less than 1 - 5 mm wide 19 Leaves less than 1 mm wide; silicula densely hairy, ± inflated at base 10. haynaldii 19 Leaves 1 mm or more wide; silicula usually glabrous 1. aizoides 17 Style 3 mm or more in fruit 20 Silicula flat 21 Leaves ciliate, otherwise glabrous; silicula usually glabrous 1. aizoides 21 Leaves ±hispid-setose all over; silicula usually densely setose 6. athoa 20 Silicula inflated 22 Leaves less than 1 - 2 mm wide; silicula 4—7(— 11) mm 3. aspera 22 Leaves 1 -2-2 mm wide; silicula 3-4 mm 4. scardica

1 Annuals, biennials or perennials usually with ± leafy stems, sometimes scapose; flowers white or cream

23 Annual(sometimesoverwintering); stylelessthan0 -3mm,

or absent

24 Fruitingpedicelsshorterthansilicula 41. lutescens 24 Fruitingpedicelsas longas or longerthansilicula

25 Silicula glabrous; cauline leaves cordate at base, amplexicaul 39. muralis 25 Silicula usually hairy; cauline leaves cuneate at base, not or scarcely amplexicaul 40. nemorosa 23 Perennial,morerarelybiennial; styleusuallymorethan

0-3 mm

26 Stemglabrous

27 Petals white; leaves ± oblong 35. fladnizensis 27 Petals yellow when young; leaves oblong-spathulate

42. crassifolia 26 Stemhairy(sometimesonlysparselyso)

28 Style 1 -2 mm in fruit 26. stellata 28 Style less than 1 mm in fruit

29 Stem robust, usually more than 10 cm, with more than

4 cauline leaves; silicula often somewhat twisted

38. incana 29 Stem more slender, often less than 10 cm, with (0)l-4(-7) cauline ieaves; silicula usually straight

30 Leaves densely clothed with very small stellate hairs only; a few cilia present (Arctic) 27. nivalis 30 Unbranched and branched hairs present on leaves; stellate hairs present or not

31 Silicula hairy

32 Leaves linear, keeled, rigid (Spain) 15. dedeana 32 Leaves lanceolate to obovate, not keeled, soft in texture

33 Whole plant canescent with a dense stellate tomentum

34 Silicula with stellate hairs only, strongly inflated

37. cinerea 34 Silicula with many unbranched or branched hairs,

only slightly inflated 34. tomentosa 33 Plant not canescent; stellate hairs relatively sparse

35 Often scapose; silicula 3-6(-7) mm 28. norvegica 35 Rarely scapose; silicula (6-)7-l 2 mm 36. daurica 31 Silicula glabrous (or with sparse cilia)

36 Stem with minute stellate hairs only (rarely with a few unbranched or branched hairs) 36. daurica 36 Stem with hairs of various types, always including some branched ones

37 lnfructescence corymbose or subcapitate

38 Silicula glabrous 29. subcapitata 38 Silicula hairy 30. cacuminum 37 lnfructescence ± elongate

39 Fruiting pedicels suberect; infructescence therefore very narrow (Arctic and mountains ofN. Europe)

28. norvegica 39 Fruiting pedicels erecto-patent; infructescence therefore broader (mountains of C. & S. Europe)

40 Pedicels and upper part of stem glabrous

31. carinthiaca 40 Pedicels and stem at least sparsely hairy

41 Rosette-leaves coarsely toothed 33. kotschyi 41 Rosette-leaves entire 32. dubia