THE FOSSIL OSMUNDACE^E. 761 



have been extremely narrow and very rare. Figs. 3, PL I., and 4 and 5, PI. II., 

 illustrate the manner in which most of the leaf-traces, if not all, left the stele ; and 

 reference to the longitudinal sections (PI. II., figs. 6-8) will make it clear that no 

 medullary ray is caused by the departure of the xylem of the leaf-trace, and that the 

 continuity of the deeper portion of the xylem ring is undisturbed. The xylem strand of 

 the leaf- trace, when immediately outside the stele, appears to have a median adaxial 

 group of protoxylem, but it is very indistinct, and once the xylem of the leaf-trace has 

 joined on to that of the stem it can no longer be recognised with certainty. It is not 

 accompanied by parenchyma as in the living Osmundacese, and must have died out 

 almost at once. 



The xylem ring consists of tracheides alone, without any admixture of parenchyma. 

 It is on an average about six or seven elements thick, and the tracheides undergo a marked 

 decrease in size towards without. As seen in transverse section (PI. II., fig. 9), most 

 of the tracheide walls have a curious speckled appearance, owing to the presence of 

 certain small black masses in their substance : two or even three of these black marks 

 may occur in the same wall. The same fact was noted by Penhallow in Osmundites 

 skidegatensis (1), and he points out that it is also to be observed in Osmunda and 

 Todea. The examination of the living genera shows at once that these markings are 

 due to the presence of more than one vertical series of pits on the same wall of the 

 tracheide. The solid unpitted parts of the wall between the several series of pits give 

 rise to the marks seen in transverse section. In Todea Barbara, Osmunda cinnamomea ,. 

 etc., the small outer tracheides show typical scalariform markings, but in most of the 

 larger ones the single series of pits on the vertical walls is replaced here and there by 

 two or even three series (PI. II., figs. 10-11). In Osmundites Dunlopi the pits seem 

 to have been more or less oval, and in one of the leaf-traces which was cut obliquely 

 the general suggestion is of porose pitting (PI. II., fig. 12), but in the stem the tracheides 

 are not sufficiently well preserved to make sure of the real nature of their marking. 

 Unfortunately, the small fragment which was available for longitudinal sections was the 

 worst preserved portion of the specimen, and the tracheides showed no markings whatever. 



There is no trace of cell-structure left in the pith or in the region of the stele just 

 outside the xylem. In one of the sections, however, the stele is surrounded at a short 

 distance from the xylem ring by a circle of small black marks and dots which un- 

 doubtedly represents the endodermis, and consists of the remains of the more persistent 

 parts of its walls. A similar endodermis also clearly outlines the leaf-traces as they 

 pass through the destroyed inner cortex (PI. II., fig. 13). In this region the leaf- trace 

 is elliptic or at most slightly reniform in section, and its xylem strand has the same form 

 with somewhat enlarged ends. The outline of the leaf-trace remains the same even in 

 the sclerotic outer cortex, but its xylem strand becomes rather more curved, and a 

 median adaxial group of protoxylem now becomes quite distinct. 



