Psilophycus W.A.Nelson, Leister & Hommersand, 2011

Holotype species: Psilophycus alveatus (Turner) W.A.Nelson, Leister & Hommersand

Original publication and holotype designation: Nelson, W.A., Leister, G.L. & Hommersand, M.H. (2011). Psilophycus alveatus gen. et comb. nov., a basal taxon in the Gigartinaceae (Rhodophyta) from New Zealand. Phycologia 50(3): 219-231.

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Description: Plants densely clustered from a crustose base with each upright consisting of a short cylindrical stipe and up to 12 orders of narrow, compressed, dichotomously divided canaliculate branches that terminate in revolute tips. Growth multiaxial by means of transversely and occasionally obliquely dividing apical cells that produce long files of parallel filaments that comprise the medulla and diverging filaments that form the cortex; cells of the primary medullary filaments linking laterally by secondary pit connections at the time of cell elongation, such that the medullary filaments are aligned in longitudinal rows and connected laterally to form rectangular networks; secondary filaments one cell long, produced from recently elongated medullary cells and growing diagonally through the intercellular matrix and linking by a secondary pit connection to a medullary cell in an adjacent cell row; cortical filaments deflected at approximately a 45u angle at maturity, infrequently branched and composed of 810 ellipsoidal cells that link to one another and to medullary cells at the base of each file by secondary pit connections. Gametophytes dioecious, the spermatangia initiated in clusters of two to five cells from terminal cells on all sides of the fertile branches and forming shallow pits surrounded by protruding sterile cortical filaments. Procarps borne along the margins and convex surface at the curve of the revolute growing tip, derived by successive concavo-convex divisions of surface cells to produce a supporting cell bearing a single cortical filament and a curved three-celled carpogonial branch with the carpogonium sitting directly above the supporting cell, which may function as an auxiliary cell; fusion of the carpogonium with the auxiliary cell not observed; cortical cells above the auxiliary cell cutting off small-celled filaments in rosettes after presumed fertilization; medullary cells interior to the auxiliary cell undergoing intercalary divisions transversely, with each resulting cell producing a rosette of small cells; gonimoblast filaments issuing from inner side of auxiliary cell and branching radially into the interior of the thallus, the gonimoblast cells elongating and penetrating between the short-celled modified medullary cells; carposporangia borne in unbranched or branched chains three to five cells long, developed either directly from gonimoblast cells, or the gonimoblast filaments fusing with modified medullary cells that, in turn, produce the carposporangial chains. Cystocarps subspherical, emerging from the lateral margins and convex side of the thallus behind the curved tips; inner pericarp composed of secondary filaments absent, the mature gonimoblasts naked, surrounded by an envelope composed of a thick outer cortex and stretched primary medullary filaments that converge to form a central ostiole; mature carpospores released progressively through the ostiole and replaced by new carposporangial chains as the cystocarp increases in girth. Tetrasporangia rarely encountered, borne in separate plants in sori, mostly on the convex side of the last five orders of branches; tetrasporocytes intercalary, transformed from primary cortical filaments in unbranched or branched chains with secondary filaments absent; tetrasporangia cruciately divided.

Information contributed by: Original description.. The most recent alteration to this page was made on 2016-03-16 by M.D. Guiry.

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

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Contributors
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=51156

Citing AlgaeBase
Cite this record as:
M.D. Guiry in Guiry, M.D. & Guiry, G.M. 16 March 2016. AlgaeBase. World-wide electronic publication, National University of Ireland, Galway. https://www.algaebase.org; searched on 22 November 2024