Rissoella J.Agardh, 1849

Lectotype species: Rissoella verruculosa (A.Bertoloni) J.Agardh

Original publication: Agardh, J.G. (1849). Algolosgiska bidrag. Öfversigt af Kongl. Vetenskaps-Adademiens Förhandlingar, Stockholm 6: 79-89.

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Type designated in: Schmitz, F. (1889). Systematische Übersicht der bisher bekannten Gattungen der Florideen. Flora oder Allgemeine botanische Zeitung 72: 435-456, pl. XXI.

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Description: Plants reach 10-20 cm in height, are erect from discoid holdfasts, and consist of flattened, linear, sometimes spirally twisted fronds fringed with marginal teeth and processes. Cystocarps and tetrasporangia scattered over the frond surfaces. Mollion et al. (1986) analyzed the carrageenans and found that most are a new type, which they named "omega" carrageenan. The RISSOELLACEAE is a monospecific family restricted to the Mediterranean Sea. Plants are multiaxial and composed of a filamentous medulla surrounded by a pseudoparenchymatous inner cortex of apparently secondarily pit-connected cells. Carpogonial branches are 2-3-celled, the basal cell capable of bearing a sterile lateral branch. Carpogonial branches are directed laterally or inwardly and have reflexed trichogynes. Aggregations of carpogonial branches occur in the inner cortex in association with a single prominent auxiliary cell and numerous cortical cells that give rise to short, branched files of nutritive cells. Early gonimoblasts develop thallus inwardly, the mataure cystocarp being composed of a richly branched central fusion cell bearing chains of cells nearly all of which become carposporangia, the carposporophyte jacketed by a thick ostiolate pericarp lacking an inner filamentous hull. Spermatangia are located in cortical pits surrounded by paraphyses. They bud off acropetally, the closest similarities being to Harveyella mirabilis and certain spore types of fungi, according to Schotter (1964). Tetrasporophytes are isomorphic with gametophytes and produce terminally attached zonate tetrasporangia in thge outer cortex, the sporangia being borne on l-2-celled stalks.

Information contributed by: G.T. Kraft. The most recent alteration to this page was made on 2021-03-14 by M.D. Guiry.

Taxonomic status: This name is of an entity that is currently accepted taxonomically.

Most recent taxonomic treatment adopted: Schneider, C.W. & Wynne, M.J. (2007). A synoptic review of the classification of red algal genera a half a century after Kylin's "Die Gattungen der Rhodophyceen". Botanica Marina 50: 197-249.

Comments: Distribution: Endemic to the Mediterranean Sea, generally in mid-littoral rocky habitats (Furnari 1985).

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Some of the descriptions included in AlgaeBase were originally from the unpublished Encyclopedia of Algal Genera, organised in the 1990s by Dr Bruce Parker on behalf of the Phycological Society of America (PSA) and intended to be published in CD format. These AlgaeBase descriptions are now being continually updated, and each current contributor is identified above. The PSA and AlgaeBase warmly acknowledge the generosity of all past and present contributors and particularly the work of Dr Parker.

Descriptions of chrysophyte genera were subsequently published in J. Kristiansen & H.R. Preisig (eds.). 2001. Encyclopedia of Chrysophyte Genera. Bibliotheca Phycologica 110: 1-260.

Linking to this page: https://www.algaebase.org/search/genus/detail/?genus_id=38737

Citing AlgaeBase
Cite this record as:
M.D. Guiry in Guiry, M.D. & Guiry, G.M. 14 March 2021. AlgaeBase. World-wide electronic publication, National University of Ireland, Galway. https://www.algaebase.org; searched on 29 November 2022

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