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XXVI. — On Old Red Sandstone Plants showing Structure, from the Rhynie Chert 
Bed, Aberdeenshire. Part III. Asteroxylon Mackiei, Kidston and Lang. 
By R. Kidston, LL.D., F.R.S., and W. H. Lang, D.Sc., F.R.S., Barker 
Professor of Cryptogamic Botany in the University of Manchester. (With 
Seventeen Plates.) 
(Read December 1, 1919. MS. received December 1, 1919. Issued separately May 11, 1920.) 
Introduction. 
Asteroxylon Mackiei was a plant of more complicated organisation and larger 
size than either Rhynia or Hornea, which have been described from the silicified 
peat-bed at Rhynie in the two preceding papers of this series.* The generic name 
refers to the stellate outline of the xylem of the stem as seen in cross section, 
while the specific name commemorates the original discovery of the plant remains 
by Dr Mackie. t 
The remains of Asteroxylon, though abundant, are unfortunately fragmentary, 
and caution is therefore necessary in mentally reconstructing the plant as it grew. 
The descriptions in this paper, though grouped as naturally as possible, are founded 
on isolated portions of a plant of considerable size. A large number of sections of 
the chert containing Asteroxylon have been examined, and there is reason to believe 
that the chief facts have been ascertained. While, however, we have a fuller know- 
ledge of Asteroxylon than of most extinct plants, any fortunate block of the chert 
may supply data to complete or qualify the account given here. In anticipation 
of this, care has been taken to keep the statement of our observations as objective as 
possible. The mutual relations of the parts, and the probable habit of the plant, will 
be discussed at the close of the descriptive portion of the paper. 
Asteroxylon was first seen in a few loose blocks of the chert discovered by Dr 
Mackie. It has since been found in specimens taken from the section of the bed 
exposed in situ by Mr David Tait, and represented on p. 762 of Part I. Remains of 
Asteroxylon have been met with in the upper portion of the bed labelled A" 1 , in bed 
A" 2, and in the upper six inches of bed B. The other blocks of the chert containing 
Asteroxylon have been found loose. 
The most abundant and generally distributed parts are shoots of various sizes, 
the stem bearing numerous leaves. The central cylinder of these stems had a solid 
xylem, which was star-shaped in cross section, and gave off small leaf-traces from 
* Trans. Roy. Soc. Edin., vol. li, p. 761, and vol. lii, p. 603. 
f Mackie, W., “ The Rock Series of Craigbeg and Ord Hill, Rhynie, Aberdeenshire,” Trans. Edin. Geol. Soc., 
vol. x, pp. 205-236, pi. xxiii. 
TRANS. ROY. SOC. EDIN., VOL. LII, PART III (NO. 26). 
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