Genus Helianthemum Spach
Род 503 (2). ЖЕЛТАК — HEJLIANTHEMUM SPACH
Spach, Ann. Sci. Nat. 2 (Bot.), VI (1836) 360; Hetianthemum subg. Ortholobum Willk., Icon. Descrл. P1. II (1856) 83Fam: Cistaceae Juss.
Genus: Helianthemum Spach
English Name: Rock rose, Sunrose or FrostweedDescription:
Semi-shrubs or annual herbaceous plants. Leaves opposite, with stipules. The flowers 2 - 20 in simple or branched, scorpion-like curved at the top clustered inflorescences, rarely single, apical, with bracts, odorless. The calyx of 5 leaflets, the outer 2 attached more or less to the corresponding inner leaflets; always narrower and shorter than the latter. Petals 5 or absent (sometimes in cleistogamous flowers); longer or shorter than the inner sepals, lemon yellow, yellow or orange. Stamens 5 - 17, single-row or numerous (30 - 100), multi-row, equal or shorter than the styles; all stamens with anthers. Ovary single-celled or incompletely trifoliate, with three wall placentas (often disappearing upwards), with 2 - 12, less often with more erect seminal vesicles on each wall placenta; style short, straight or elongated, ascending; stigma like a spherical head. The box is triangular, three-part, almost one-nested, the walls are not hardened. Seeds small, without seam, often multi-walled, with almost central, just folded germ. Insect-pollinated or self-pollinating (cleistogamous); propagated by seeds.
Table for determination of the species
1 Semi-shrubs; petals longer than inner sepals .................................................................... 1. - H. mimmularium (L.) Mill.
1* Annual plants; petals shorter than the inner sepals ............................................................................................................ 2
2 The inner sepals are membranous, bubbly swollen in the fruit ............................................... 4. - H. aegyptiacum (L.) Mill.
2* The inner sepals are grassy, the fruit is not bubbly swollen .......................................................................................... 3
3 In the case of the fruit, the flower stalks are horizontally spread out or curved upwards ……. ............................................. ……………………..…………................................................................................................ 3. - H. salicifolium (L.) Mill.
3* At the fetust, the flower petioles are upright .................................................................. 2. - H. lasiocarpum Desf. ex Willk.
¹ Developed by M. Markova.From: „Флора на Н Р България”, том VII, Изд. на Б А Н, София, (1979) * * * * *
Helianthemum /ˌhiːliˈænθɪməm/,[1] known as rock rose, sunrose, rushrose, or frostweed,[2] is a genus of about 110[3] species of flowering plants in the family Cistaceae. They are widely distributed throughout the Northern Hemisphere, especially in the Mediterranean.[3]
New World species formerly classified as Helianthemum have been transferred to genus Crocanthemum.[4][5]Description
These are usually shrubs or subshrubs, and some are herbaceous annuals or perennials. The leaves are oppositely arranged, but some plants may have alternately arranged leaves along the upper stems. The flowers are solitary or borne in an array of inflorescence types, such as panicles, racemes, or headlike clusters. The flower has three inner sepals and two smaller outer sepals. It has five petals usually in shades of yellow, orange, or pink. The style at the center is tipped with a large stigma. The fruit is a capsule containing many seeds.[3]
Ecology
Helianthemum are known to form symbioses with mycorrhizal fungi. In the Mediterranean they are associated with Terfeziaceae, the desert truffles. Together, plant and fungus may have a beneficial effect on the arid local landscapes, preventing soil erosion and desertification. Some symbiotic pairs include Helianthemum salicifolium and the truffle Tirmania nivea, and H. guttatum and T. pinoyi.[6]
One of the most commonly observed mycorrhizae on Helianthemum is a member of a different family, Cenococcum geophilum. This fungus is not host-specific, and it often associates with oaks, as well. Some studies suggest that Helianthemum and oaks growing together in a habitat may "share" their mycorrhizae.[7]
Helianthemum are food plants for the larvae of some Lepidoptera species, such as the large grizzled skipper and the silver-studded blue.[8] The leaf miners Bucculatrix helianthemi and B. regaella both feed exclusively on Helianthemum sessiliflorum, as does Coleophora eupreta. C. ochrea is limited to Helianthemum, and C. bilineella and C. potentillae have been observed on the genus.
From Wikipedia, the free encyclopedia * * * * *
References: „Флора на Н Р България”, том VII, Изд. на Б А Н, София, (1979), Wikipedia, the free encyclopedia
Distribution in Bulgaria: (Conspectus of the Bulgarian Vascular Flora) = conspectus&gs_l= Zlc.
Distribution:
SPECIES:
Helianthemum nummularium (L.) Mill. - Common rock-rose
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