THE FOSSIL OSMUNDACE^E. 473 



distinctly thicker, the protoxylem strand divides as before, but the outer portion of 

 it which passes into the thickened end of the xylem strand becomes mesarch before it 

 is nipped off with the branch trace (fig. 31, br.). 



The Roots. 



In the specimen that consisted of the compacted coating of leaf-bases numerous 

 roots are to be seen boring their way outwards through the tissues of the stipules. 

 When they reach the region where the leaf-bases have become disintegrated they 

 bend downwards and form a zone consisting almost entirely of vertically running 

 roots (figs. 2 and 3, R.). The roots are fairly large, but their diarch xylem strands 

 are narrow, with rather sharp-pointed protoxylems (fig. 32, prx.). The cortex is 

 stout and consists of an inner zone of thin-walled elements very much crushed and 

 an outer zone of cells with firmer walls which become fairly thick-walled towards 

 without. The peripheral two or three layers of the cortex consist of markedly 

 smaller cells than the others. 



The Sporangia. 



A few isolated sporangia were found in the matrix of the peat-like mass which 

 undoubtedly belong to our plant. They possess a multiseriate annulus forming a 

 curved band of at least three cells in width (fig. 33) and ten to twelve cells in length 

 (figs. 33 and 34). These two figures make it clear that the sporangium was of the 

 Osmundaceous type, with a vertical line of dehiscence beautifully indicated by the 

 narrow elongated cells in fig. 33. 



Remarks. 



Judging from the arrangement of the sclerenchyma in the stipular leaf-base, 

 Osmundites spetsbergensis stands very near to the recent species Osmunda Clay- 

 toniana, which is also characterised by the possession of two specialised masses of 

 sclerenchyma at the two sides of the sclerotic ring and a continuous strand of the 

 same in the stipular wings.* So far as is known, Osmunda cinnamomea is the only 

 other species in which the sclerenchyma of the sclerotic ring is of this heterogeneous 

 type, but it differs from both the above in having a third specialised mass in the 

 median line on the abaxial side and also in having its stipular sclerenchyma broken 

 up into separate strands (I.e., fig. 11). 



With regard to its foliage Osmundites spetsbergensis is, on the other hand, almost 

 identical with Osmunda regalis, with which plant Nathorst originally compared 

 it t (text-fig. 2). Nathorst also placed it in the modern genus Osmunda, but it 

 seems to us advisable to include it in the fossil genus Osmundites, on the grounds 

 that it does not agree in complete detail with any of the existing species, and that 

 we are at present in entire ignorance as to the structure of its stem. It must be 



* Trans. Roy. Soc. Edin., vol. xlv., pi. vi. figs. 11 and 12, 1907. + Nathorst, I.e., p. 382. 



