184 Mr J. M. Macfarlane on LepidopMoios. 



plant, quite distinct from both UloJendron and Lcpidoden- 

 dron. In the strata of the Calciferous Sandstone and 

 Carboniferous Limestone series of the Lothians and Fife, 

 LepidopJdoios laricinum is exceedingly common. Selecting 

 for description typical examples of stems, say 6 inches in 

 diameter, we find that the surface of the bark is covered 

 with a series of leaf-cushions, broadest at their bases, 

 slightly tapering to the cicatrix, and imbricating over one 

 another in a doivnivard or reversed direction (PL VIII. 

 fig. 3). At the apex of each cushion is situated the leaf- 

 scar or cicatrix, having a rhomboidal outline, and bearing 

 the impressions of three fibro-vascular bundles, which 

 proceeded out into the leaf. Though I have not been able 

 to obtain leaves still attached to the cicatrices, they are 

 very abundant in the isolated state ; in the limestone of 

 Burdiehouse, for example, slabs are sometimes so covered 

 with them as to obscure the impressions of other organisms 

 present. They are linear acute, and traversed by a single 

 strong well-marked midrib. Corda* figures a very fine 

 specimen with leaves attached. We are indebted to him 

 for a careful account of the internal anatomy of the stem, 

 which has been further expanded by Williamson. The 

 centre is occupied by a mass of cellular tissue forming a 

 true pith; surrounding this is a zone of scalariform vessels, 

 forming what Williamson designates "the medullary 

 vascular cylinder" ; outside this is another zone, which he 

 asserts is formed by exogenous growth ; this he terms 

 " the ligneous zone." Piercing it we have medullary rays, 

 while outside is a mass of cellular tissue, surrounded by 

 prosenchyma ; and, lastly, there is a sub-epidermal and 

 epidermal cellular tissue. I have not been able to study 

 its microscopic structure, as, with the exception of the bed 

 mentioned, pieces well preserved for this purpose are very 

 rare in our district. The variations in the appearance of 

 the bark are interesting. My esteemed preceptor. Professor 

 Balfour, f in pointing out the changes which the bark layers 

 oi Araucaria imbricata may assume, very truly remarks, 

 " There can be no doubt that in vegetable palasontology 

 the number of species has been needlessly multiplied, any 



* Lib. cit. tab. 1, fig. 1. \ Palueo. Butauy, 1872, p. 8. 



