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XXIV. — On Old Red Sandstone Plants showing Structure, from the Rhynie Chert 
Bed, Aberdeenshire. Part II. Additional Notes on Rhynia Gwynne-Vaughani, 
Kidston and Lang; with Descriptions of Rhynia major, n.sp., and Hornea 
Lignieri, n.g., n.sp. 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 Ten Plates.) 
(Read July 8, 1918. MS. received May 17, 1919. Issued separately January 20, 1920.) 
Introduction.. 
In Part I * a general account was given of the silicified peat-bed found at 
Rhynie, and one vascular plant was described in detail under the name of Rhynia 
Gwynne-Vaughani. Further study has shown that there are two species of Rhynia 
which we now distinguish as Rhynia Gwynne-Vaughani and Rhynia major. The 
account in Part I applies to both these species. Along with them there occurs a 
plant of similar grade of organisation to Rhynia , though quite distinct from that 
genus: this we name Hornea Lignieri. Asteroxylon Mackiei, on the other hand, 
which will be described in the next part, was a plant of larger size and much more 
complex morphology. 
We are thus now able to establish the existence and main features of four archaic 
Vascular Cryptogams from the Rhynie bed. In the present paper additional notes 
on R. Gwynne-Vaughani are given, and R. major and Hornea Lignieri described 
in detail. In conclusion, the morphological bearings of the facts will be briefly 
considered. 
Our former paper was based mainly on sections prepared from loose blocks of the 
chert, and partly from specimens collected from the chert bed in situ. The material 
for the present paper was mostly obtained in position in the chert bed, though a few 
loose blocks have yielded valuable information. 
Rhynia. 
As mentioned above, two species of Rhynia have to be distinguished. Their simi- 
larity in organisation is so great that they are not always readily separated from one 
another, and in our former paper they were described together under the name Rhynia 
Gwynne-Vaughani. The second species, which we now separate as Rhynia major, 
is larger in all its parts, and differs from R. Givynne-V aughani in the absence of 
hemispherical projections and adventitious branches from the stems, in the greater 
size of the stele and xylem strand, and in the much larger size of the sporangia 
and spores. 
* Trans. Boy. Soc. Edin., vol. li, 1917, p. 761. 
TRANS. ROY. SOC. EDIN., YOL. L1I, PART III (NO. 24). 
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