198 Prof. W. C. Williamson and Dr. D. H. Scott. [June 13, 



forming medullary wood and bast, with inverted orientation. This 

 is precisely the anomaly shown by certain species of Tecoma, and 

 other dicotyledons. The anomalous medullary cambium is con- 

 tinuous with the normal cambium through the leaf-trace gaps. This 

 case is a striking instance of the independent appearance of the same 

 structural peculiarity in families as remote as possible from each 

 other. 



B. The Leaf. 



1. Connexion between Leaf and Stem. New and conclusive evidence 

 has been found, confirming the conclusion previously arrived at (in 

 Mem. XVII), that " Eachiopteris aspera" is the petiole of Lygino- 

 dendron. In several specimens petioles with the characteristic struc- 

 ture of that fossil, are found inserted on the stems of Lyginodendron. 

 The vascular bundles on leaving the pericycle of the stem bend out 

 rapidly into the base of the leaf, becoming concentric at the same 

 time. Petioles, continuous with the Lyginodendron stem, have been 

 traced up to the point where they begin to ramify. 



2. Form of the Leaf. The petioles, which we now know to belong 

 to our plant, branch repeatedly, and ultimately give rise to small 

 palmately-segmented leaflets. The leaf was thus a highly compound 

 one, and we can confirm the statement previously made, that the 

 character of the foliage was that of Brongniart's form-genus 

 Sphenopteris. 



3. Structure of the Petiole. The most important point here is that 

 throughout the petiole and rachis, the vascular bundles, of which 

 either one or two are present, are of typical concentric structure, as 

 in a fern. 



The cortex of the petiole has essentially the same structure as that 

 of the stem. 



4. Structure of the Lamina. We have examined sections of leaflets 

 (found in connexion with petioles of Lyyinodendron), in which the 

 structure is perfectly preserved. The lamina had a distinctly bifacial 

 structure, with well-differentiated palisade, and spongy parenchyma. 

 Stomata have only been observed on the lower surface. The vascular 

 bundles in the lamina appear to have been collateral, as is also the 

 case in recent ferns. 



5. On a Peculiar Bud-like Structure. This is a unique specimen, 

 consisting of an axis, of obscure structure, bearing numerous append- 

 ages which exactly resemble the Avell-known cortical outgrowths of the 

 stem and petiole of Lyginodendron. At first sight, the specimen bears 

 some resemblance to a cone, but it was more probably a bud or young 

 leaf, from which the inner delicate tissues have perished, leaving the 

 protective outer coat, bearing the appendages, which may represent 

 the bases of palese. 



