4 Nutrition
4.3 Results
4.3.1 Intestinal contents
4.3.1.1 Plant remains
A large part of the plant material consists of peridermal (cork) tissue (pers. obs., confirmed by WILDE pers. comm.). This is to be found in all of the three studied specimens with intestinal contents. The flattened, layered and highly ordered rows of cell walls are clearly recognisable (Fig. 66). The regular arrangement of cells originates from synchronous cell divisions of the "Phellogene" in the cork-cambium. The latter is divided in the inner Phelloderm, which is rich in chloroplasts and in the outer cork tissue (Phellem, SITTE et al. 1998). This is an extemal tissue built of dead cells, the cell walls are covered with an impermeable suberine layer. Suberine is a substance
consisting of highly polymerised esters and unsaturated fatty acids. This suberine layer is additionally permeated by wax (SITTE et al. 1998, RAVEN et al. 1988). Fig. 66C-G show the abundant and well developed pit-canals (for intercellular transport) in the form of small peglike protuberances (pers. obs.) which are typical for peridermal tissue (WILDE pers. comm.).
Plant cuticula is preserved in all of the three specimens (Fig. 67), although it is
relatively rare. In SMNK-PAL 381 3 there is only one fragment, which can be identified as such a cuticular remain (Fig. 67s). But no stomata are recognisable in all of the cuticular fiagments. The absence of these hints towards a cuticula originating from the peridermal tissue, in contrast to a leaf cuticula. Fig. 67F+R show layers of peridermal tissue situated below the cuticula. According to WILDE only three structures are
potential stomata (Fig. 67T-V), although only the one figured in Fig. 67T can safely be identified as a stoma.
Cornmon structures in the plant material are fragments of twigs or stalks (Fig. 68), they are preserved in the specimens WDC-C-MG 12211 23 und SMNK-PAL 3 8 13. The cells are elongated (prosenchymatic) and remains of conducting elements, wood
respectively phloematic fibres can safely be identified (WILDE pers. comrn., Fig. 68Q-T ). Probably the circular cell walls thickenings of the conducting elements were preserved in this case. Fig. 68B, C, E and G picture prosenchymatic cells. Fig. 68E shows the preserved cell wall, cell lumen and its cast.
The specimens WDC-C-MG 1221123 and SMNK-PAL 38 13 additionally seem to contain sclerenchymatic tissue (Fig. 69), the largest amount of which is preserved in the first specimen. Large amounts of this tissue would hint towards seeds or fhits (WILDE pers. comm.). Sclerechymatic tissue also contains numerous and well developed pit-canals. These are here preserved as small pegs as well, because the interior of the cell is casted. According to WILDE (pers. comm.) this is a typical preservation of plant cells in Messel. The mechanisms leading to this result remain enigmatic. As a rule, sclerenchymatic tissue appears to be less ordered than cork tissue. Both cell types are
C h a ~ t e r 4: Nutrition - 1 69
more or less isodiametric. Sclerenchymatic cells often show lignified secondary cell walls and act as important stabilising elements. The thick secondary cell walls contain many characteristic, simple pit-canals (RAVEN et al. 1988). In SMF-ME 35 16 only isolated cells with pit-canals are identifiable (Fig. 69V+W). Fig. 69W shows the cross section of a cell with the incorporated pit-canals. With the preservation found in the investigated specimens, it is difficult to distinguish sclerenchyrnatic tissue from peridermal tissue. According to WILDE (pers. cornm.) it seems more likely that this tissue partly represents cork, resp. peridemal tissue, as well.
The structures depicted in Fig. 70 represent fragrnents of a seed or fruit husk. A complex wall composed of sclerenchymatic cells is visible. The layer consisting of fibres arranged in a zigzag pattem (Fig. 70E+F) most probably has a stabilising function (WILDE pers. comm.). The tissue in cross section shows prosenchymatic cells with a large number of pit-canals (Fig. 70G). The upper face bears pores (Fig. 70A+B). This characteristic tissue was only found in WDC-C-MG 12211 23.
Additionally there are some plant remains which can be characterised by cells showing a distinct "bubbly" or "foamy" inner structure (Fig. 71). They probably represent dead cells which were filled with organic secretions in the living plant. Unfortunately, the nature of these secretions cannot further be characterised, but it could have been resin, ethereal oils or tannic acids. This foamy structure is a preservational mode which is probably caused by processes of chemical separation which are not completely
understood to date. Such cells occur generally in parenchyme or peridermal tissue and it is very likely that the tannic acids were produced in these cells (WILDE pers. comm.).
These structures were also preserved in the prosenchymatic cells of the conducting elements (Fig. 68A+B). These structures were found in the specimens WDC-C-MG 1221123 and SMNK-PAL 3813.
In the specimen WDC-C-MG 1221123 one type of pollen was found, bearing a characteristic "spiny" sculpture and possessing at least two apertures (Fig. 72).
According to WILDE (pers. cornrn.) these pollen belong to the Juglandaceae (walnut family), which represented a main part of the Eocene forest surrounding Lake Messel. In two cases, four pollen were found in a single plant remain. This possibly hints to catkins of Juglandaceae, which have already lost most of their pollen. The pollen have
characteristic, bulge-like folds (Fig. 72B-D, J+M) and bear three pores
(SCHAARSCHMIDT 1992). AS all of the pollen are still situated in plant tissue, all three pores are not visible. In Fig. 72F two pores are recognisable, while Fig. 72C, M+N shows one of the pores.
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Fig. 66: Peridermal (cork) tissue found in the intestinal contents of WDC-C-MG 1221123, SMF ME 3516 and SMNK-PAL 3813. The flattened, layered and highly ordered cell rows are clearly
recognisable. A-I: From WDC-C-MG 1221123. J-Q: From SMF ME 3516. R-X: From SMNK-PAL 3813. C-G: Abundant and well developed pit-canals in form of small peglike protuberances, typical for peridermal tissue. D: Enlargement of C. P: Enlargement of 0. V: Enlargement of U. SEM.
Fig. 67: Plant cuticula and a few isolated stomata found in the intestinal contents of WDC-C-MG 1221123, SMF ME 3516 and SMNK-PAL 3813. The absence of stomata hints towards a cuticula originating from peridermal tissue, in contrast to a leaf cuticula. A-L: From WDC-C-MG 1221123 with the most abundant cuticula remains, M-R: From SMF ME 3516. S: From SMNK-PAL 3813.
This is the only identifiable fragment of cuticula in this specimen. T-V: Potential isolated stomata found in the intestinal contents of WDC-C-MG 1221123. D: Enlargement of C. F+R: Layers of peridermal tissue are situated below the cuticula. SEM.
Fig. 68: Fragments of twigs or stalks found in the intestinal contents of the specimens WDC-C-MG 1221123 and SMNK-PAL 3813. The cells are elongated and remains of conducting elements (wood resp. phloematic fibres) can be found. A-0: From WDC-C-MG 1221123. P-X: From SMNK-PAL 3813. B,C,E+G: Elongated (prosenchymatic) cells. R: Enlargement of Q. Q-X: Wood resp.
phloematic fibres. SEM.
Fig. 69: Sclerenchymatic tissue, containing numerous and well developed pit-canals found in the intestinal contents of the specimens WDC-C-MG 1221123, SMNK-PAL 3813 and SMF ME 3516.
The cell types are more or less isodiametric. A-H: WDC-C-MG 1221123. I-U: SMNK-PAL 3813.
V+W: From SMF ME 3516, only isolated cells with pit-canals are preserved. B: Enlargement of A.
J: Enlargement of I. L+M: Enlargement of framed areas in K showing cell lurnina with distinct pit- canals. P, R+T: Enlargements of framed areas showing cells with peg-like preserved pit-canals. W:
Cross section of a cell with casts of pit-canals. SEM.
Fig. 70: Fragments of a seed or fruit husk from found in the intestinal contents of WDC-C-MG 1221123. B: Enlargement of A, face with pores. D: Enlargement of C, a complex wall of
sclerenchymatic tissue is visible. E+F: Fibres are arranged in a zigzag pattern, most probably for stabilisation. G: Tissue in Cross section, prosenchymatic cells with a large number of pit-canals are present. SEM.
Fig. 71: Cells with a distinct bbbubbly" or "foamy" inner structure, probably representing organic secretions such as ethereal oils or tannic acids. This structure is probably caused by processes of chemical separation which are not yet completely understood. A-H: from WDC-C-MG 1221123. I- 0: from SMNK-PAL 3813. Arrows and enlargements show probably peridermal cells filled with this characteristic structure. SEM.
Fig. 72: Pollen belonging to the Juglandaceae (walnut family) found in the intestinal contents of WDC-C-MG 1221123. They have a characteristic "spiny" sculpture, bulge-like folds and at least two apertures. A+I: Fragments of probable catkins. B-E: Enlargements of A. J-M: Enlargements of I. H: Enlargement of framed area in G. B-D, J+N: Pollen showing the characteristic bulge-like folds. F: Pollen with two recognisable pores. C, M+N: Pollen with one visible pore. SEM.
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