THE FOSSIL OSMUNDACECE. 477 



as a puzzling and unaccountable anomaly. Indeed, the whole construction of the 

 stem of Osmundites Carnieri is highly suggestive of that of 0. Skidegatensis, except 

 that in the latter there is no internal endodermis, although a well-developed internal 

 phloem is present (I.e., PL V. figs. 24 and 27). Unfortunately, in Osmundites Carnieri 

 no trace of the phloem is preserved even on the outside of the stele, where it un- 

 doubtedly must have existed. Although there is rather less space left for it between 

 the endodermis and the xylem on the inside of the vascular ring than on the outside, 

 it is probable that the phloem followed the endodermis all round the inner surface of 

 each separate meristele as well as on the outer. If this should be proved to be the 

 case, Osmundites Carnieri would be shown to possess the first and only dictyostelic 

 stem yet discovered in the Osmundacece. Further, when Osmundites Skidegatensis 

 is taken into account, it suggests that in the past the Osmundacece have attempted 

 an advance in their stem anatomy along lines of their own in the direction of a 

 polycyclic vascular system such as has been attained in other orders of the Filicales. 



The cortex of the stem is very wide, constituting about a third of its whole 

 diameter (30 mm.). It appears to consist of an inner parenchymatous and an outer 

 sclerotic cortex, but the preservation is too imperfect to show the relative proportions 

 of the two zones. Numerous leaf-traces are cut across in their passage out through 

 the cortex. They are large and distinctly curved even in close proximity to the 

 stele. Nevertheless they remained arch-shaped throughout, and their extremities are 

 not curled inwards even in those nearest the periphery of the stem (fig. 35, It.). 



The Roots. 



The root steles arise from the leaf-traces and continue to do so even when the 

 latter are far out in the cortex. They depart from the back of the leaf-trace in the 

 median plane. One root, however, was seen to arise directly from the stele of the 

 stem. They obtain a cortex of their own soon after their departure. In the region 

 of the root coating they possess a very stout and broadly oval diarch xylem strand 

 (fig. 39). The outer region of the cortex was thin-walled and has disappeared, leaving 

 a clear zone in the matrix to indicate its former presence. Within this comes a zone 

 of dense, thick- walled cells. 



Locality. — " Auf dem Wege von Villa Rica nach der Siedelung Mbuvevo in zwei 

 Bachen nahe am Fusz des Gebirges." South Paraguay. 



Horizon. — Uncertain. According to Schuster, the age limit of the beds under 

 discussion lies between the Jurassic and the Tertiary. 



Osmundites sp. 



This specimen, communicated to us by Professor M. Benson, was in such a poor 



state of preservation that the vascular system was almost completely destroyed 



throughout the fossil and no detailed description of its structure is possible. 



TRANS. ROY. SOC. EDIN., VOL. L. PART II. (NO. 16). 68 



