Horneophyton sporangia
deutsche Version

Horneophyton, one of the early land plants preserved in the Rhynie chert, has often been described with drawings far off reality, as already mentioned in
Rhynie Chert News 15 . 
So it may be appropriate to show a few more details here.Horneophyton sporangium
Certainly the sporangia are not shaped as shown in an often reproduced schematic drawing [1] but it is not easy to produce a more typical one since the shape can vary greatly.
There is
one feature which is characteristic for Horneophyton: It is a kind of column inside the sporangium, called columella. It may be forked or branched, with every branch belonging to a protrusion of the complex-shaped sporangium.
What is seen in Fig.1 is either a simple-shaped sporangium with uncommonly short and thick columella or part of a more complex one. 
The obtuse angle between the two sporangia in Fig.2 may be compared with such angle on a forking columella as, for example,
in [2] or RCN 15, Fig.5. There may have been a common cause in either case. It is thinkable that forking or multiply branched sporangia evolved from adjoining sporangia as in Fig.2 by fusion. 

Fig.1: Horneophyton sporangium, or part of it, with broad columella. Image width 4.3mm.

Fig.2 (below): Horneophyton sporangia, adjoining, with broad columellas. Image width 7mm.

Horneophyton sporangium
 


The baroque shape in Fig.3 is apparently due to shrinkage of the wall of the empty sporangium.



Fig.3 (below right): Horneophyton sporangium of uncommon aspect, empty. Image height 5.5mm, same scale as Figs.1,2.
Horneophyton sporangium












horneophyton sporangium




Fig.4 (left): Horneophyton sporangium
with spores, 60Ám. Image width 1.7mm.

With the higher magnification in Fig.4, the spores, 60Ám, some of them still stuck in tetrads, are seen well preserved while the sporangium is in a state of decay.
Well preserved spores of
Horneophyton are also seen in [3].

Samples:
Fig.1: Rh11/61.3,  Fig.2: Rh23/1.3,
Fig.3: Rh7/23.1,    Fig.4: Rh13/14.1.

H.-J. Weiss     2019 (Dec.)

[1]  D.A. Eggert : The sporangium of Horneophyton lignieri.   Amer. J. Bot. 61(1974), 405-413.
[2]  W.El-S. El-Saadawy, W.S. Lacey: The sporangia of Horneophyton lignieri ..., Rev. Pal. Pal. 28(1971), 137-144.
[3]  H. Steur: steurh.home.xs4all.nl
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