Launaea arborescens

Primary tabs

http://media.bgbm.org/erez/erez?src=EditWP6/photos/Launaea_arborescens_Bb_04.jpg

Description

Dense, intricate, spinescent, ± irregularly hemispherical shrub, c. 50-100 (-150) cm high, almost leafless, with a deep-reaching strong taproot and strong lateral roots; roots shoot bearing. Branches terete, divaricately and intricately branched with subulate spinescent terminal segments; young branches lignified and glaucous, with ± succulent cordex becoming greyish-brown with age. Latex whitish and of unpleasant smell. Leaves rosulate to crowded at the base of the innovations, usually somewhat succulent, glaucous-green, narrowly spathulate to ± linear in outline, acute, (0.8)2-5(8.5) long, either 0.1-0.5 cm wide and entire to scarcely sinuate-dentate, or pinnatifid with few linear to narrowly triangular segments and then up to 1.5-2(4) cm wide, soon deciduous, higher up the shoots reduced to inconspicuous, ovate-acute bracts. All innovations terminated by a divaricately branched, spinescent synflorescence with branchings in their majority enclosing an angle of 80-100°; capitula always situated terminal and single on the subulate, 0.5-2(3) cm long peduncles, which after shedding of the capitula persist as spines. Capitula with 7-19 flowers. Receptacle at fruiting time 1.5-2.5 mm in diameter. Involucre (7.5)8.5-12(15) mm long, towards fruiting time cylindrical to conical, at time of fruit dispersal involucral bracts star-wise outspread and their midrib swollen and hardened in lower half; outer involucral bracts 4-7, ± imbricate, with narrowly scarious margin, the outermost broadly ovate(-acute), 1-2 mm long and ± equally wide, the following bracts gradually longer and more lanceolate, the innermost lanceolate, 1/2-3/4 as long as the inner involucral bracts; inner involucral bracts, particularly in mainland populations, variable in number, 5-6(8), linear- lanceolate and of ± equal length, 7-12 x 1.5-3.5 mm. Flowers with a bright yellow ligule of 5-8 x 2.1-2.8 mm and a tube 4.4-7.2 mm long; anthertube without appendages 2.6-3.8 mm long, basal and apical appendages 0.4-0.6 mm long. Achenes (2.5)3-4(4.8) x 0.7-1.3 mm, prismatic, all with 5 main ribs accompanied by 2 secondary ribs, with ± distinct, transverse, roundish, ± tuberculate wrinkles, often somewhat pulverulent-papillose; inner slender cuneate, (pale) brown: marginal somewhat curved and slightly compressed, distinctly thicker and cuneate, (dark) brown. Pappus 5-8 mm long, subhomomorphic, of numerous setaceous rays gradually somewhat decreasing in diameter from centre to periphery.

from: Kilian, N. 1997: Revision of Launaea Cass. (Compositae, Lactuceae, Sonchinae). – Englera 17.

Distribution

Africa: Algerianative (AlgerianativeA,B,C); Canary Is.native (Canary Is.nativeD); Cape VerdenativeE; Madeiranative (MadeiranativeD); Mauritanianative (Mauritanianative); MorocconativeA,B,F,G,H; Western SaharanativeI Europe: Spainnative (SpainnativeJ,K,L,M)

Ecology

[...] a xerophyte chiefly confined to semidesert vegetation types. An annual mean precipitation above 400 mm and a minimum temperature below 0 °C delimit its distribution in SE Spain [...]. This largely holds true also for NW Africa as its abscence from the more humid areas [...] indicates. [...] Inland populations [in NW Africa] are most frequently confined to wadi beds and certain habitats in mountain areas.

from: Kilian, N. 1997: Revision of Launaea Cass. (Compositae, Lactuceae, Sonchinae).- Englera 17: 151-157.

Bibliography

A. Frankenberg, P. & Klaus, D. , Atlas der Pflanzenwelt des Nordafrikanischen Trockenraumes: Computerkarten wesentlicher Pflanzenarten und Pflanzenfamilien. 1980
B. Ozenda, P., Flore du Sahara, ed. 2. 1977
C. Quézel, P. & Santa, S., Nouvelle flore de l'Algérie et des régions désertiques méridionales 2. 1963
D. Hansen A. & Sunding P., Flora of Macaronesia. Checklist of vascular plants. 4th revised edition in Sommerfeltia 17. 1994
E. Kilian in Englera 17. 1997
F. Jahandiez, E. & Maire, R., Catalogue des plantes du Maroc 3. 1934
G. Nègre, R. , Petite flore des régions arides du Maroc occidental 2. 1962
H. Valdés, B., Rejdali, M., Achhal El Khadmiri, A., Jury, S. L. & Montserrat, J. M., Catalogue des plantes vasculaires du Nord du Maroc, incluant des clés d’identification 2. 2002
I. N. Kilian in Englera 17. 1997
J. Bolos, O. de & al., Flora manual dels països catalans. 1990
K. Bolòs, O. de & Vigo, J., Flora dels països catalans 3. 1995
L. Tutin, T. G. & al., Flora Europaea. 1964-1993
M. Willkomm, M., Supplementum Prodromi florae hispanicae 2. 1893 (as Sonchus freynianus)