Herbivore deterrence by early land plants
deutsche Version

There are seven species of early land plants known from the Rhynie chert. Two of them, Trichopherophyton and Nothia, deter herbivores by quite different means. The means of Trichopherophyton is obviously mechanical: A combination of short and long pointed bristles would frustrate any crawling creature trying to get at the sporangia with the nutritious spores (Fig.1). 

Figs.1-3: Trichopherophyton cross-sections, same scale, frame widths 8.5, 5.5, 4 mm).

Lots of short bristles and a few stiff long ones are present in Fig.1. The length of some bristles may exceed the diameter of the shoot:
Rhynie Chert News 95 .
The quite unusual formation in Fig.2 looks like an intimate contact of yet unseen creatures with tentacles: Two unlike specimens of Trichopherophyton, the bigger with 
tentacles waving about, the smaller with short ones around its surface, had grown, while clinging together, in a water-filled cavity in the silica gel. Subsequently, silica gel did not only accumulate in their tissue but also outside so that the two specimens became fused into a common solid cylindrical column still free-standing in the cavity, with quartz crystals around, as still seen in Fig.2 with a dark shadow on the right indicating a gap left over from the original cavity. It would be interesting to know whether this formation is purely incidental or rather hiding a secret.
Trichopherophyton Trichopherphyton
Figs.4-6: Trichopherophyton
cross-section details,
same scale,
frame widths 2, 1.4, 0.7 mm.
Magnification 4 times that of Figs.1-3.

Like the sizes of the bristles, their connection to the  epidermis cells is variable. Long bristles emerge from broad bases often filled with small cells (Fig.6) with sizes comparable to those of the smallest epidermis cells in Fig.5. Of similar sizes are some faintly seen meshes on a Trichopherophyton tip cross-section in Fig.4. The left one of the two bristles in Fig.5 seems to consist of tiny grains much smaller than the cells.
It may be mentioned here that microbial colonies in decaying organic matter can make unexpected structures known as pseudo cells: Rhynie Chert News 112. This phenomenon will be considered with repect to Trichopherophyton in a separate contribution

Surprisingly different from the mechanical means of deterrence
as applied by Trichopherophyton is the subtle means of hidden poison in Nothia.

Fig.7: Two spore capsules of Nothia incidentally cut such that the essential features are seen. Frame width 4.3mm.
Fig.8: Drawing related to Fig.7
Fig.9: Nothia cross-section with big tubes between small cells near the boundary. Frame width 4mm.

2 Nothia sporangiaNothia sporangium Nothia cross-section
As a highly improbable coincidence, the chert sample in Fig.7 has been cut such that two sporangia are seen on the cut face with the essential features clearly visible. The object below right is easily recognised as a capsule with complex wall structure and an opening above right. This opening is really a curved slot running over a larger part of the capsule so that it can appear as a narrow gap between two parts of the capsule above left. (See Rhynie Chert News 110.)  Incidentally this capsule is cut such that big tubes, cut across or lengthwise, are clearly seen on the two lids.
The tube cross-sections on the sporangium section below right are less distinctly seen but highly interesting. A very few of them reveal faint residues of a decayed cellular structure inside: in Fig.8 near the top of the drawing. This faintly seen residue had given rise to the suspicion that the big tubes are no giant cells for water storage as generally assumed [1] but vessels designed for a more sophisticated purpose.
The recent euphorbias make long tubes from ordinary cells by dissolving cell walls with the purpose of storing a sticky poisonous milk there. Probably Nothia had invented the same trick of tubes releasing deterrent liquid if tapped by creatures trying to get at the tasty spores. The surface tension of liquids can be dangerous to
small creatures which are not able to free themselves from a drop. A tube under pressure would spill its liquid content profusely and soil the biting creature with possibly fatal effect [2]. Also it can be assumed that Nothia, too, had stored a repulsive liquid in its tubes.
Rh3/18.4: found in 1998, Fig.9;         Rh2/21 (2.8kg): found in 2001, Part2, Fig.7;
Rh15/78.2: obtained from Barron in 2014, Figs.1,3,5,6;        Rh14/18.2,3: obtained from Barron in 2007: Figs.2,4;

H.-J. Weiss    2021  

[1] H. Kerp, H. Hass, V. Mosbrugger: New data on Nothia aphylla,
      in: P.G. Gensel, D. Edwards (eds.): Plants Invade the Land, N.Y. 2001.
Rhynie Chert News 33  
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