Gundelia

small plant in flower
Gundelia tournefortii is a spiny hemicryptophyte with stems 20–100 cm high, that branch from the base, the first growth of the plant consists of a rosette of leaves. All parts contain a milky latex. The parts above the surface break from the root and may be blown away by the wind as a tumbleweed, assisting in the dispersion of the seed. All counts executed sofar arrive at eighteen chromosomes (2n=18).
Root, stems and leavesEdit
The plant develops a woody, vertical rootstock of up to 4 cm in diameter, at the surface usually covered by the remains of old leaves. The leaves are sessile or decurrent at their base with spiny wings, and alternate set along the stems. The lowest leaves are usually 7–30 cm long and 4–16 cm wide, pinnately dissected and the sections of the larger leaves may be pinnately parted themselves, and have a dentate or serrate margin, all tipped with spines. The midvein and sideveins are prominent, whitish, sometimes tinged purple. The leaf surface may be covered in spiderweb-like hairs, that tend to wither away quickly.
InflorescenceEdit
  tumbleweed-stage
The stem divides into ten or more branches, each of which is topped by a compound spiny ovoid inflorescence of 4–8 cm in diameter, which may be covered in dense arachnoid hairs. This inflorescence is unusual for members of the family Asteraceae, as each true flowerhead is so far reduced as to only contain one floret, which is surrounded by its own involucre. Five to seven of these monofloral flowerheads combine into secondary flowerheads, each subtended by a spiny bract hardly or substantially longer than the secondary flowerheads, with only the centre floret developing a cypsela, and the surrounding ones only producing pollen. These secondary flowerheads later break free from the globose assembly of flowerheads that sit on the end of each branch of the stem during the tumbleweed-stage. Remarkable for a member of the tribe Cichorieae are also the disk florets, a trait that is further only present in Warionia saharae.
FloretsEdit
The pentameric corollas are usually 7–10  mm long, gloomy purple or yellowish outside, white to bright yellow, greenish, flesh colored or silvery to red purple inside, with spreading narrow lobes of 3–4 mm mm  long  and about 1 mm wide, the tube hairless inside. The five merged anthers form a cylinder of 4–6  mm long, yellow or brownish in color. The style arms are also brownish.
PollenEdit
Pollen is covered in acute spines.

Fruit and seedEdit
The involucral bracts of the secondary flowerheads are merged into a brown, durable, hard cup with a fibery fringe. Each contains only one cypsela of about 8 mm long, 5 mm at its widest, somewhat dorsally compressed, narrow at its base and widest beyond halflength, with the pappus at its tip consisting of a 2 mm high cup, narrowest at its base.
Characters common to all AsteraceaeEdit
Like in all Asteraceae, the pentameric flowers have anthers that are fused together forming a tube through which the style grows. The style picks up the pollen on hairs along its length and splits into two style branches at its tip. These parts sit on an inferior ovary that grows into an indehiscent fruit in which only one seed develops (a so-called cypsela). All florets (in this case only one) are set on a common base (the receptacle), and are surrounded by several rows of bracts, that form an involucre. A particular character of Gudelia that is rare among the Asteraceae is that florets are gender specialised, with the central floret being functionally hermaphrodite and the marginal florets being functionally male.
Characters common to CichorieaeEdit
Tumble thistles are assigned to the Cichorieae-tribe that shares anastomosing latex canals in both root, stem and leaves, and has flower heads only consisting of one type of floret. In Warionia and Gundelia these are exclusively disk florets, while all other Cichorieae only have ligulate florets. Gundelia is unique in the complex morphology of the inflorescences.

Differences with other generaEdit
Warionia and Gundelia share a thistle-like appearance, anastomosing latex-ducts, floral heads that only contain disk florets, spurred anthers, and styles with branches and highest part of the scape covered with long hairs. Gundelia however is herbaceous, has monofloral primary flowerheads combined into groups of five to seven, the centre floret hermaphrodite, the marginal florets functionally male, and those groups combined in ovoid spiny florescences at the end of the stem, and spiny leaves, florets dull yellow to dull purple on the inside, purple to rusty on the outside. Warionia is a shrub, has many dandelion-yellow florets in each flowerhead, single or with two or three together at the end of the branches, the leaves dentate but not spiny.Scolymus is also a thistle-like herbaceaceous perennial with anastomosing latex-ducts, related to Gundelia, but it has many yellow, orange or white ligulate florets in each flowerhead, which are arranged with many in a spike-like inflorescence, or with a few at the end of the stems.

PhytochemistryEdit
Gundelia contains several essential oils, with large proportions (20-25% each) of thymol and germacrene-D.

Gundelia

Gundelia

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