A particular connection of alga tubes
deutsche Version

What looks like a special connection of tubes in this sample of Rhynie chert seems to be a severely deformed contact site between the adhering tube-like cells of the charophyte alga Palaeonitella.
tube connection
Image: Seldom seen phenomenon of uncommon contact area of what seems to be adhering tube-like charophyte alga cells. Image width 1.5mm.

With the conspicuous pairs of spheres in mind, which are occasionally seen in the chert, the idea suggests itself that the bloated ends of the adjacent cells seen here could have been an early stage of the formation of spheres in pairs.
It is known that Palaeonitella can grow spherically bloated cells under the influence of some parasitic fungus [1].
The fact that the structure shown here is extremely rare while big spheres in pairs may be seen by the dozen in one chert sample leads to the tentative conclusion that it is a short-lived transient stage while the spheres are persistent by design. This would be compatible with the observation that the pairs of spheres are often seen without any attached alga since the alga could have decayed before silicification while the spheres persisted. Also it would favour the interpretation of spheres in pairs as alga formations but not as fungus chlamydospores.
It must be admitted that the conclusions derived here from this one and only formation of this type may be not quite convincing. Other suggestions for an explanation would be welcome. 
Picture taken from a sample in the collection of Steffen Koehler, Meissen, collected decades ago by Brian Beveridge, Gloucester,
                on the now protected site formerly owned by A.G. Lyon, Rhynie, documented here under the label Rh2/303.1 .

H.-J. Weiss      2018

[1] T.N.Taylor, M. Krings, E.L. Taylor:
Fossil Fungi. Elsevier 2015, p.64.


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