NAME Oochytrium lepidodendri
AGE Late Carboniferous.   AGE span: 318.1...299 mya
K&J CLASSIFICATION (2000) Chytridiomycetes, Chytridiales.
FIGURE(S)
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FIGURE REFERENCE Renault B. 1896. Bassin Houiller et Permien d' Autun et d'Épinac, Flore Fossile, pt. I; Études des gîtes minéraux de la France, Paris, Fascicule 4, 578 p.
SPECIES, AUTHORITY O. lepidodendri Renault 1896, p. 424, figs. 78, 79.
LOCATION France.
ORIG DESCRIPTION* As is well known, the woody core of Lepidodendrons is perfectly solid, without a trace of cellular tissue, and formed by striped tracheids of which the ornamentation has been preserved in the finest detail, at least when they did not have to suffer the ravages of microphytes that are present in large numbers.

In the interior of the vessels, one can observe a number of multiseptate filaments [rhizohyphae], some simple, others branched several times, of various length; these are clearly mycelia [rhyzomycelia] in various stages of development. In many of these the main branch terminates in an ovoid blister or bulblet, of which the larger axis averages 12-15 µm in length, the shorter one 9-10 µm. Some are spherical, detached, 13 µm across, and possibly to be considered resting spores. The ovoid bulblets are of various size; many are rather smaller, apparently not yet having reached their mature size. Many, also, are free; these appear to have been torn loose, and accumulated in considerable numbers inside certain vascular cells, of which they fill almost the entire interior cavity.

Certain hyphae appear to produce more than one bulblet, placed at their extremity. When well preserved, the mycelia are shown to be composed of 6-7 µm long cells, demarcated by distinct septa. The cells close to a sporangium are shorter, and darker in coloration.

The sporangium wall is rather strongly cuticularized, brown, and of very regular form. One of its extemities, to be considered as its base, is attached to a piece of mycelium of quite variable length; the opposite extremity is provided with an orifice surrounded by a rim and apparently closed by an operculum.

Not uncommonly, sporangia appear to be affixed to the vessel wall by a rather short piece of their mycelium.

Most of the sporangia are filled; sometimes the protoplasm fills the entire cavity; other times it has contracted into a spherical mass that is not everywhere in contact with the sporangium wall. In this latter mass, one may see some granulation, which possibly simulates a cellular structure.

Several sporangia are open, and appear to let escape a stream of zoospores.

Mixed up with these sporangia there may be a few spherical objects of nearly the same size, with a fine roughness to their outer surface; possibly these represent cysts [resting sporangia?].
COMMENTS* This form, found in the young branches of Lepidodendron esnostense, appears to be related to the Chytridiales, apparently to the tribe Endogenes [?], given the shape of the sporangia, their manner of dehiscence, and their position near the end of the hyphae. It doesn't fit the descriptions of any of the modern genera, such as Olpidium, Olpidiopsis, Rozella, Woronina, Claochytrium, etc.

W. Smith described other chytrid fungi from woody cores and roots of Lepidodendrons from the British Coal Measures, e.g. Peronosporites antiquarius, and Protomycetes protogenes.
PUBLICATION REFERENCE Renault B. 1896. Bassin Houiller et Permien d' Autun et d'Épinac, Flore Fossile, pt. I; Études des gîtes minéraux de la France, Paris, Fascicule 4, 578 p.
K&J REMARKS Kalgutkar and Jansonius (2000) did not transfer this species to Palaeomycites, because the description, figures, and indicated affinity, all point toward a classification with the Order Chytridiales. Palaeomycites now contains a variety of forms, all more or less incomplete; Oochytrium has a well described mycelium [rhizomycelium], as well as fructifications [eucarpic], that do not warrant it to be lumped with Palaeomycites. If the two genera were to be merged, Oochytrium would have priority.

In Chytridiales, a true mycelium is lacking, but in eucarpic forms (like Oochytrium lepidodendri) a system of rhizoids (so-called "rhizomycelium") is present as an integral part of the thallus. Rhizoids are root-like, filamentous, finely branched and tapering extensions of the chytrid thallus.
TYPE
ALL NAMES (Including synonyms) Oochytrium lepidodendri
SERIAL NUMBER 1164
PUBLIC COMMENTS
 *For source, see Publication Reference.