THE FOSSIL OSMUND ACE^E. 475 



Osmundites Carnieri, Schuster. 

 (PL XLIV. figs. 35-40.) 



1911. Osmundites Carnieri, Schuster, Berichte den Deutsch. Bot. Gesellsch., Bd. xxix. p. 534, 

 pis. xx. and xxi., text-figs. 1, 2, and 3 (inaccurate). 



An account of this species is included in this memoir although it has already been 

 dealt with by Schuster, owing to the fact that some points in its structure have been 

 misinterpreted in the original description and several important structural details 

 have been overlooked. 



As represented in this specimen, Osmundites Carnieri differs strikingly in its 

 structure from the customary Osmundaceous stocks by the complete absence of the 

 coating of leaf-bases. This is replaced by a coating of densely packed adventitious 

 roots, 35 mm. or more in thickness, which immediately surrounds the actual stem of 

 the plant. In the greater arboreal Osmundacece the sheathing bases of the leaves 

 no doubt persisted around the upper region of the stem, but towards the base they 

 rotted away and became disintegrated, their place being taken by the downward- 

 running roots which in the lower regions formed an increasingly thick coating round 

 the stem. It follows that the relative proportion of sheathing leaf-bases and of root 

 coating present in any section will depend upon the height above the base at which 

 the section has been taken. In the light of these considerations the specimen of 

 Osmundites spetsbergensis previously described on page 470 came from a transitional 

 region towards the upper end of the stock, whereas that of Osmundites Carnieri came 

 from a level somewhere near the base. 



The stem itself is unusually large (fig. 35), about 90 mm. in width, and includes 

 an enormous stele 35 mm. in diameter ; more than a third of the total width of the 

 stem. The stele contains a ring of no fewer than thirty-five free and distinct strands 

 of xylem which present all the differences in form that are typical of the modern 

 Osmundacece and in consequence require no detailed description. These xylem strands 

 are, however, unusually deep, including about fifty-five tracheae from the inside of 

 the strand to its outer margin. Their peripheral elements are not conspicuously 

 smaller than those lying towards within. The larger tracheae appear to possess 

 multiseriate pits (fig. 40, tr.), while the smaller are scalariform. The pith is very 

 extensive, but too imperfectly preserved for any opinion to be formed as to its true 

 nature. 



The stele is surrounded on the outside by a very distinct line of delimitation 

 formed by one or rarely two layers of dark, thick-walled cells (figs. 35 and 36, o.en.). 

 These cells are no doubt the equivalent of the endodermis. This endodermis and 

 in consequence the whole stele is interrupted by the departure of each leaf-trace, 

 which leave unusually wide gaps. The outer endodermis turns inward round the 

 margins of the leaf-gap and passes along the sides of the xylem strands that border it 



