Riccia
Riccia huebeneriana
The star liverworts ( Riccia L.) is a genus within the order Marchantiales. Worldwide, over 150 species of the genus, whose distribution center located in areas with a Mediterranean climate embossed. The European representatives can be divided ( with air chambers ) and Riccia by the appearance of air chambers in the two subgenera Ricciella.
Description
Riccien are small, living on earth or in the water liverworts, among which there are both annuals and perennials. The thallus consists of repeatedly dichotomously branched segments, resulting in the formation of the characteristic rosettes or semi- rosette shape. Partial are formed at the edges of papillae or cilia. The fabric can either be of a loosely organized assimilation tissue made from a mostly broken epidermis, or it is formed from a continuous epidermis underlying compact cell lines without further differentiation. All species of the genus lack the otherwise characteristic of many liverworts oil body. The antheridia and archegonia are scattered sunk in the thallus. The mature spores are released only by the decay of the thallus. 32-1350 spores with a diameter of 40-200 microns are produced per capsule. A key feature is the determination in some species the number and size of the air chambers on the spore surface dar.
Dissemination
The genus is cosmopolitan spread. Its distribution focus is, however, in areas with a Mediterranean-influenced climate, where the center of diversity of the genus is. It is essential for the occurrence of the genus is the change from dry and wet periods. In tropical areas without drying times the genus therefore missing.
Ecology
Riccia species grow mainly on bare soil sites with mineral surface. Here, soils with a very good water-holding capacity, such as clay and clay soils, colonized preferred. Almost all species are relatively weak competitors pioneer species that depend on regular disturbance. Such conditions are common in man-made sites such as Lands or periodically dry covered ponds to find. Others, such as Riccia cavernosa occur on regularly flooded alluvial soils along rivers. In areas with arid and semi- arid conditions, the ecology of there occurring Star liverworts changes significantly. The species are mostly perennial and annual and no longer have adaptations to desiccation and heat on. Main features are often heavily pigmented thalli against the high radiation intensity, the curl of the thalli with dehydration, as well as the ability to years of persistence in a dried state. In such areas, species of the genus Riccia are associated with other liverworts, lichens and algae and form together with these biological crusts, which play a significant role in reducing erosion. In Central Europe the species occur mainly in pond soil and stubble arable companies. In slightly acidic to subneutralen, damp stubble fields species of the genus in a liver moss rich expression of the association are Pottietum truncatae Waldheim to find 1944. In more oceanic climates dominated a society with Riccia sorocarpa, Entosthodon fascicularis and partially Sphaerocarpos species ( Riccio sorocarpae - Funarietum fascicularis Lec. , 1978) is to be found. On pond soils is mainly the Riccio cavernosae - Pseudephemeretum nitidi All. ex v. Hübschm. 1957 spread.
Types (selection)
The genus can be divided into five subgenera, of which the sub-genera Riccia and Ricciella are represented in Central Europe. Their central European representatives are listed below.
- Subgenus Riccia with compact, undifferentiated tissue Riccia ciliifera
- Riccia gougetiana
- Riccia michelii
- Riccia ciliata
- Riccia intumescens
- Riccia sorocarpa
- Riccia papillosa
- Riccia beyrichiana
- Riccia glauca
- Riccia bifurca
- Riccia gothica
- Riccia subbifurca
- Riccia trabutiana
- Riccia warnstorfii
- Riccia ligula
- Riccia crozalsii
- Riccia crustata
- Riccia lamellosa
- Riccia melitensis
- Riccia macrocarpa
- Riccia sommieri
- Riccia breidleri
- Riccia bicarinata
- Riccia atromarginata
- Riccia canaliculata
- Riccia cavernosa
- Riccia duplex
- Riccia
- Riccia huebeneriana
- Riccia rhenana
- Riccia frostii
- Riccia crystallina
- Riccia perennis