Cistroses

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The cistus (Cistus) form a plant genus in the family of cistus (Cistaceae). They have a significance as useful plants, as medicinal plants and as ornamental plants.

In part, the types of non-monophyletic! genus Halimium taxed or subsumed under Cistus.

Description

Vegetative characteristics
Cistrose species are highly branched, bushy shrubs, half-shrubs or dwarf shrubs, some of which produce an aromatic resin, ladanum. The oppositely arranged foliage leaves are seated or stalked. The leaf spreads are simple. Auxiliaries are missing. The shrubs are perennial and can reach more than 3.50 m altitude. The shapes of the leaves are elliptical, lancet-shaped or linear. The surface of all-round leaves can be rough, velvety, felty, smooth-gloss, leathery and sticky. The leaf colour may be whitish, yellowish, light green to dark green. The smell of the leaves can be resinous-spicy.

Generative characteristics
The finite or lateral inflorescences are zymös, bearing-oldig or wrap-like, occasionally also reduced to a flower.

The twilight flowers are radiarly symmetrical and five-fold, as in almost all species from the order of the Malven-like (Malvales). The two outer chalice leaves are at least as large as the three inner or missing. The short-lived crown leaves are already wrinkled in the bud. Usually there are five in the number, but occasionally also four or six. The crown leaves are white, white-yellow or light pink to purple, in some species, especially hybrid species, they are yellow or dark red spotted on the ground. The diameter of the flowers is usually between 5 and 7 cm. The 50 to 200 yellow stamens are arranged in several rows and all fertile. Usually five, rarely six to twelve fruit leaves have grown into a five-, rarely six to twelve-fold fruit knot. The seed plants are orthotropic.

The wooden capsule fruits jump almost completely along the fan walls. The numerous seeds are polygonal.

Chromosome sets
The basic chromosome number is n = 9. All species of which chromosome counts exist are diploid with 2n = 2x = 18 chromosomes.

Occurrence

The genus is common throughout the Mediterranean and the Canary Islands. The greatest biodiversity is found in the Western Mediterranean (France, Spain, Portugal, Morocco, Algeria). The cistroses form a main component of the garigue. They usually grow on dry, stony areas, partly also in clear forests of the Mediterranean hardleaf vegetation or the Canary pine forests, sometimes on calcareous and nutrient-poor soils.

Systematic classification

The genus Cistus was erected in 1753 by Carl von Linné in Species Plantarum in volume 1 on page 523. Type species is Cistus crispus

Species

White cistrose, (Cistus albidus), Syn.: Cistus tomentosus, Cistus vulgaris: (lat: al)