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XXXIL — On Old Red Sandstone Plants showing Structure, from the Rhynie Chert 
Bed, Aberdeenshire. Part IV. Restorations of the Vascular Cryptogams, 
and Discussion of their bearing on the General Morphology of the Pteridophyta 
and the Origin of the Organisation of Land-Plants. By R. Kidston, LL.D., 
D.Sc., F.R.S., and W. H. Lang, D.Sc., F.R.S., Barker Professor of Cryptogamic 
Botany in the University of Manchester. (With Five Plates.) 
(Read May 2, 1921. MS. received May 2, 1921. Issued separately August 26, 1921.) 
This part of the account of our examination of the plants preserved in the 
silicified peat-bed of early Old Red Sandstone age found at Rhynie will be devoted 
to the consideration of a number of general questions concerning the four Vascular 
Cryptogams which it has yielded. 
1. In the first place the morphological characters of Rhynia Gwynne-V aughani , 
R. major, Hornea, and Asteroxylon will be reviewed and the attempt made to 
reconstruct the external appearance of these plants as they grew. In relation to this 
a few additional features of the plants will be described. 
2. This will lead naturally to a consideration of the general bearings upon plant- 
morphology of the facts mentioned in this series of papers. 
Reconstructions of the External Morphology of the Vascular 
Plants of the Rhynie Deposit. 
The structure of the various parts of the four Vascular Cryptogams found in the 
Rhynie peat-bed has been described in the three preceding Memoirs of this series. * 
In each case proofs or indications of the connection of the parts have been mentioned 
and discussed. The chief features are summarised in the diagnoses of Rhynia 
Gwynne-Vaughcmi, Rliynia major, and Hornea Lignieri in Part II, and of 
Asteroxylon Mackiei in Part III ; these descriptions need not be repeated. 
The reconstructions on Pis. I and II represent our conception of the external form 
and relative sizes of the four plants. The absence of specimens preserved as 
impressions necessitate such reconstructions being to a certain extent imaginative. 
This especially applies to the more complex plant of Asteroxylon. Even for this, 
however, and certainly in the cases of the simply constructed sporophytes of the 
Rhyniacese, the reconstructions probably give a fairly correct idea of the habit of 
the plants. 
The brief notes that follow will serve to indicate both those features in the 
reconstructions for which we possess clear and direct evidence, and those which have 
to be supplied more or less conjecturally. The opportunity will be taken to add 
* Trans. Roy. Soc. Eclin., vol. li, p. 761 ; vol. lii, pp. 603, 643. 
TRANS. ROY. SOC. EDIN., VOL. LII, PART IV (NO. 32). 
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