Taraxacum Weber
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https://doi.org/10.5281/zenodo.293764 |
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persistent identifier |
https://treatment.plazi.org/id/90236A28-9C44-F543-FD08-FAAD1D9E4C95 |
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treatment provided by |
Plazi |
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scientific name |
Taraxacum Weber |
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173. Taraxacum Weber View in CoL 1
Perennial herbs with tap-root. Stems few to many, simple. Leaves all basal, entire to laciniate-dentate or lobed. Capitulum solitary, often flat-topped. Involucral bracts in 2 rows, glabrous or ciliate; inner erect, more or less linear; outer shorter, usually wider, often with paler margins, sometimes with a small lump (callosed) or small appendage (corniculate) just below the apex. Receptacle more or less flat, without scales. Ligules usually yellow, often with a darker stripe beneath. Achenes fusiform to oblanceolate, often spinulose near apex, usually with a slender beak and a more or less clearly demarcated swollen region (cone) between beak and body. Pappus of many rows of simple, rough, usually white hairs.
The posture of the outer involucral bracts is of taxonomic importance and this should be ascertained when the plant is living.
Most species flower in spring or early summer; they sometimes also have a secondary flowering in autumn but then lack many of their diagnostic characters. A few species are mainly if not entirely autumn-flowering and for these this peculiarity is noted in the descriptions. Ripe achenes are necessary for the determination of the species.
Most European species of Taraxacum are apomictic polyploids (2/2 = 24, 32, 40, 48) or occasionally aneuploids (e.g. 2« = 25, 26, 27). Wholly sexual species (1-3) are always diploid (2« = 16); a few other diploid sexual species are found under 8, 24, 28 and 30. Facultative apomixis is found in a few triploid species under 24 and 30. Sexual and facultatively apomictic plants are recognizable by their small, regular pollen and often imperfect setting of seed. Obligately apomictic plants have irregular pollen (or lack pollen altogether) and set seed well. Hybrids occur rarely, and only where sexual or facultatively apomictic plants grow together, or occur with pollen-bearing apomicts.
In this account, 30 species or groups of species have been numbered and described. A selection of the more widespread of the c. 1200 species described from Europe has been listed under the groups to which they belong (though where fewer than 12 such species have been described in any group all have been listed). The index contains in addition all the species that have been recorded from Europe (with the exception of some of those in the T. officinale group); these entries are in roman type and are equated with the groups to which they belong. In the case of the T. officinale group, because of the very large number of species involved, only those which occur in Standard Floras or are especially widespread have been included.
Names of synonyms of species which do not appear in the text are given in italics in the index and equated simply with the groups to which they belong. In some cases the sectional names used in this account are nomenclaturally incorrect, but they have been retained here because they are familiar and helpful and because the correct sectional nomenclature has yet to be worked out.
Since H. von Handel-Mazzetti, Monographie der Gattung Taraxacum . Leipzig & Wien. 1907, there has been no complete monograph; most of the species have been described since this date. There is a recent monograph of the 17. T. palustre group (ftecï.Palustridfby J. L. van Soest, Acta Bot.Neerl. 14: 1-53(1965), and useful accounts of 7 and 18-22 can be found in J. L. van Soest (1969) (see below). A list of species in 24-27 is given in J. L. van Soest, A Catalogue ofTaraxacum Section Erythrosperma Dt. em. Lb. Leiden. 1966 , and these are monographed by R. Doll, Feddes Reperì. 84: 1-180 (1973).
Detailed accounts of the species in particular regions include: J. L. van Soest, Bull. Jard. Bot. Bruxelles 26(2) (1956); 31(3) (1961) (Belgium). A. J. Richards, Watsonia 9 (Suppl.) (1972) (British Isles). K. Jessen & К. Wiinstedt in C. Raunkiaer, Dansk Ekskursions-Flora, ed. 5, 302-318. Kobenhavn. 1934. (Denmark). J. L. van Soest, Veroff. Geobot. Inst. Rübei (Zürich) 42 (1969) (Switzerland). M. P. Christiansen in L. К. Rosenvinge et al., The Botany of Iceland 3(3). Copenhagen & London. 1942. (Iceland). J. L. van Soest, Acta Bot. Neerl. 4: 82-107 (1955); 6: 74-92 (1957) (Netherlands). B. K. Schischkin in E. G. Bobrov & N. N. Tzvelev, Flora URSS 29: 405-560. Leningrad & Mosqua. 1964. (U.S.S.R.). H. Dahlstedt in C. A. M. Lindman, Svensk Fanerogamflora 559-589. Stockholm. 1918. (Sweden).
Recent accounts of the cytology, micro-evolution and breeding systems in the genus can be found in A. J. Richards, New Phytol. 69: 761-774, 1103-1121 (1970) and Bot. Jour. Linn. Soc. 65: 47-59 (1972).
1 Achenes without a beak, or with a short beak not more than |
the length of body 1. glaciale 1 Achenes with a distinct beak at least J the length of body
2 Achenes without a cone, smooth or nearly so; pappus yellowish; flowering in autumn
3 Leaveslinear-lanceolatein outline; capitula15- 20 mm in diameter 2. bessarabicum 3 Leaves obovate-lanceolate in outline; capitula 30-40 mm in diameter 3. serotinum group 2 Acheneswitha cone,usuallymoreor lessrugoseor spinulose; pappus whitish; usually flowering in spring
4 Beak of achene stout, not or scarcely longer than body; leaves entire or shallowly lobed (arctic-alpine)
5 Achenes blackish; body spinulose throughout
4. phymatocarpum group 5 Achenes straw-coloured, red or brownish; body smooth or rugose
6 Achenes dark red, almost smooth 5. glabrum group 6 Achenes straw-coloured or brownish, rugose
6. pacheri group 4 Beakofachene slender,often much longerthan body;leaves usually lobed, often deeply dissected
7 Body of achene 4-5- 5 mm, smooth or nearly so
12. spectabile group 7 Body of achene 2-3-4- 5 mm, usually rugose, at least above
8 Outer involucral bracts with wide pale or scarious margins comprising at least J of area of bract
9 Leaves many, with persistent bases; outer involucral bracts with brown midrib 22. dissectum 9 Leaves few, with bases not persistent; outer involucral bracts without brown midrib
10 Leaves oblanceolate to obovate; usually autumnflowering 8. bithynicum group
10 Leaves linear to linear-lanceolate; spring-flowering
17. palustre group 8 Outer involucral bracts with at most a narrow pale or scarious margin comprising less than f of area of bract
11 Achenesreddish(red, purple, violet,reddish- or pinkishbrown)
12 Achenes with conical cone less than f as long as body
13 Achenes deep reddish-purple, with body 3-5—4 mm; leaf-lobes usually entire 7. schroeteranum 13 Achenes pinkish to pale reddish-brown, with body 2-5-3 mm; leaf-lobes dentate 14. unguilobum group 12 Achenes with cylindrical cone f-f as long as body
14 Petiole distinctly winged; ligules deep yellow
15 Achenes reddish-purple or brownish, with cone
1-1-5 mm, and beak 8-12 mm
28. hoppeanum group 15 Achenes straw-coloured, or sometimes reddish, with cone 0-6-1 mm, and beak 6-9 mm
16 Involucre usually dark, often + violet-purple, pruinose 19. nigricans group 16 Involucre green 15. croceum group 14 Petiole unwinged; ligules pale or medium yellow
17 Plant relatively robust; body of achene 3-5 mm or more 28. hoppeanum group 17 Plant slender; body of achene 2-3-3-5 mm
18 Achenes red, purple or violet
24. erythrospermum group 18 Achenes reddish-brown or pink
19 Leaves patent, deeply and narrowly lobed;
achenes reddish- or pinkish-brown
26. fulvum group 19 Leaves erect, often entire to shallowly lobed,
sometimes dissected; achenes pink or reddish
27. gasparrinii group 11 Achenesbrown, yellow, cream orgreyish, withoutred or pink tint
20 Outerinvolucralbractscorniculate
21 Leaves 3-15 cm, dissected; body of achene not more than 3 - 5 mm
22 Leaf-lobes 6-8; ligules golden-yellow, often involute; cone less than 0-5 mm, conical 23. obliquum group 22 Leaf-lobes 3-5; ligules pale to medium yellow, neverinvolute; cone more than 0-6 mm, cylindrical
25. simile group 21 Leaves 5-25 cm, entire or shallowly lobed; body of achene 3 -2-4-5 mm
23 Leaves glabrous, more or less coriaceous, not or scarcely lobed
24 Leaves dark green, obovate, not denticulate
9. obovatum group 24 Leaves grey-green, oblanceolate,denticulate
10. glaucanthum group 23 Leaves rarely glabrous, never coriaceous, usually lobed
25 Outer involucral bracts with a distinct pale margin; cone of achene 1-1-5 mm 28. hoppeanum group 25 Outer involucral bracts without a distinct margin;
cone of achene not more than 0- 8 mm
11. ceratophorum group 20 Outer involucral bracts ecomiculate, but sometimes with a slight callosity
26 Leaves with dark spots
27 Outer involucral bracts erect or appressed; body of achene more than 4 mm 12. spectabile group 27 Outer involucral bracts patent; body of achene less than 4 mm
28 Plant bright green; ligules deep yellow; cone of achene 0-6-1 mm, cylindrical 15. croceum group 28 Plant dull or dark green; ligules medium yellow;
cone of achene 0-3-0-8 mm, conical
13. praestans group 26 Leaves unspotted 29 Petioles winged;ligulesdeepyellow,orange-yellow or yellowish-brown (arctic-alpine)
30 Ligulesyellowish-brown,involute 21. cuculiatimi group
30 Ligules deep yellow or orange-yellow, flat
31 Cone of achene c. 1 mm, sub-cylindrical (arctic) 15. croceum group
31 Cone of achene less than 1 mm, conical (alpine)
32 Leaves narrow, lobed; involucre dark, often ±
violet-purple, pruinose 19. nigricans group
32 Leaves wide, entire or shallowly lobed; involucre green 20. fontanum group
29 Petioles wingedor unwinged;ligules pale or medium yellow
33 Outerinvolucralbractspatentordeflexed(rarely erect)
34 Outer involucral bracts 6-12 mm, patent, sometimes glaucous on inner face; body of achene c.
3 -5 mm 13. praestans group
34 Outer involucral bracts 11-20 mm, erect to deflexed, never glaucous on inner face; body of achene 2-5-3-5 mm
35 Robust plant of N. Fennoscandia; outer involucral bracts very pale on inner face; leaves with elongate terminal lobes; petioles pale,
wide 29. crassipes group
35 Usually on disturbed ground; variable, but without the above combination of characters
30. officinale group
33 Outer involucral bracts erect or appressed
36 Beak с. Ц times as long as body of achene; small alpine plant
37 Leaves many; leaf-bases persistent; outer involucral bracts with a brown midrib 22. dissertimi
37 Leaves few; leaf-bases not persistent; outer involucral bracts without a brown midrib
18. apenninum group
36 Beak more than If times as long as body of achene; plant of wet places
38 Body of achene 3-4 mm, brown
16. adamii group
38 Body of achene 4-5-5 mm, straw-coloured
12. spectabile group
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