344 Dr. D. H. Scott [May 15, 



were at any rate something distinct from true Ferns, as we now 

 know them. This evidence is derived from a study of the anatomical 

 structure, which in Cycads and Ferns as they now exist, is sufficiently 

 different to prevent any possible confusion between the two groups. 

 A single section from the leaf-stalk of the Fern-like Cycad Stangeria 

 would be enough to show that it is a true Cycad and no Fern, and 

 conversely, a single section from the frond of Lomaria, with which 

 Stangeria was once confused, would show it to be a true Fern and 

 not a Cycad. 



A common Coal-Measure plant, named Lyginodendron Oldhammm, 

 was one of the first of the PalsBOZoic quasi-Ferns to be examined 

 anatomically We owe this work, like so many other great advances 

 in fossil botany, to the late Professor Williamson, who thus led 

 the way to the solution of the problem which occupies us this 

 evening. 



Externally, the plant is wholly Fern-like ; its characteristic 

 highly compound foliage is that of a Sphenopteris (S. Honinghausi) 

 with a Davallia-like habit. The large fronds were borne, at intervals, 

 on a somewhat slender stem, which rooted freely. The slender 

 proportions and the presence of spines everywhere, on leaf and stem, 

 suggest that the plant may have been a scrambling climber, like 

 Davallia aculeaia, for example, among recent Ferns. 



The structure of all the vegetative parts of the plant-stem, leaf 

 and root is now known as perfectly, perhaps, as in any plant now 

 living. The leaves turn out to be true " Fern-fronds " in structure 

 as well as in external aspect. The vascular bundle traversing the 

 petiole, for example, is of the " concentric " type characteristic of 

 Ferns, and any differences there may be are in details only. 



A section of the stem, however, bears at first sight no resem- 

 blance to that of a Fern ; outside the pith, we find a broad zone of 

 wood and bast with its cells arranged regularly in radial series, like 

 that of an ordinary " exogenous " tree, and in detail approaching 

 especially the Cycadean structure. At the border of the pith there 

 are distinct strands of wood, and this region, which was laid down 

 before the radially arranged zone, recalls the structure of an Osmunda. 

 The bundles in the cortex of the stem, on their way out to the leaves, 

 have in this part of their course exactly the structure of the strands 

 in the leaf-stalk of a Cycad — a structure found, in this form, in no 

 other living plants. 



The roots, when young, resemble those of certain Ferns (Maratti- 

 acese), but as they grew older they also formed secondary wood 

 and bast like the roots of Gymnosperms. 



On the ground of this remarkable combination of structural 

 characters, it was inferred tbat Lyginodendron could not have been 

 a true Fern, but must have occupied a position intermediate between 

 the Ferns and the Cycadean Gymnosperms. 



A similar association of diverse anatomical characters has now 

 been proved to exist in various other quasi-Ferns of Palaeozoic age. 



