Scolymus

Scolymus is a genus of annual, biennial or perennial, herbaceous plants that is assigned to the Daisy family, and can be found in Macaronesia, around the Mediterranean, and in the Middle East. All species are spiny, thistle-like in appearance, with flowerheads that consist of yellow (rarely orange or white) ligulate florets, and canals that contain latex. It is known as سكوليمس (skwlyms) in Arab, scolyme in French, and is sometimes called golden thistle or oyster thistle in English. The species of Scolymus are spiny herbaceous annuals, biennials or perennials of up to 1¾ m high, that contain a milky latex. These have twenty chromosomes (2n=20). Biannual and perennial plants produce a stout taproot of up to 8 cm in diameter and 60 cm long. Young plants consist of a rosette of leaves, which may be variegated, once-pinnately spiny-lobed, to 30 cm long, and having short, fleshy stalks. The stems can be simple or carry many branches, and carry spiny wings along their lengths. The wavy leaves with prominent veins are pinnately divided and are alternately set along the stems. The leaf margin has prominent pale green or yellow veins and large teeth which are topped by fierce spines. The leaf surface may initially be covered in soft, felty hairs, which quickly clear away, most slowly on the veins. The flowerheads are seated at the end of the stem or in the limbs of the higher leaves, are arranged in a spike or a globose cluster and are subtended by two to more than five leaflike bracts. Each flowerhead is circled by an involucre that consists of many spine-tipped bracts in several rows, the outer papery and shorter than the inner ones, which are leaflike in consistency. These surround the common floral base (or receptacle), which is conical in shape and is set with ovate papery bracts called chaff or paleae. Inplanted are dorsally compressed cypselas, each enclosed by a palea, the outer rows higher than the inner ones. On top of the cypselas there may be two to five stiff scabrous bristles, which are equivalent to sepals (and are called pappus). Also, on top of the cypsela and within the pappus is a yellow, orange or white strap-like corolla which ends in five teeth, together comprising a ligulate floret. 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 are set on a common base (the receptacle), and are surrounded by several rows of bracts, that form an involucre. Golden 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 Scolymus these are ligulate florets, common to the group except for Warionia and Gundelia, which only have disk florets. A unique character setting Scolymus apart from the other Cichorieae are the dorsally compressed cypsellas which are surrounded by scales (or paleae). S. maculatus is an annual of up to 1½ m high, there are more than five leaflike bracts subtending each globose cluster of flowerheads, and these bracts are pinnately divided. The yellow florets carry some black hairs. The cypselas do not have pappus at their top (but are encased by the paleae). The spined wings along the stems are uninterrupted. Leaves have a whitish vein along their margin. S. grandiflorus is an annual or biennial of up to ¾ m high with one, two or three leaflike bracts subtending each cluster of flowerheads and these are spiny dentate. The yellow to orange florets do not have black hairs. The cypselas are topped by three to seven bristles of smooth pappus hairs (and are encased by the paleae). The spined wings along the stems are uninterrupted.