662 MR R. KIDSTON AND MR D. T. GWYNNE-VAUGHAN ON 



the free petiole the leaf-trace as a whole assumes the characteristic shape of a horse- 

 shoe. The softer tissues of the trace are very imperfectly preserved, but at some 

 points the xylem sheath and even the sieve-tubes of the phloem could be made out 

 on both sides of the xylem (figs. 64 and 65, ph.). The sclerotic ring of the petiole is well 

 developed, and is surrounded by a narrow zone of parenchyma which is prolonged at 



Diagram 3. — Diagrammatic restoration of a transverse section of an outer petiolar base of Anomorrhosa Fischeri to show the 

 arrangement of the sclerenchyma. The area within the dotted line probably becomes sclerotic at a point farther out in 

 the petiole. 



the sides into very short stipular wings (text fig. 3). Our outermost petioles were 

 too close in to show the full development of the stipules or the typical arrangement of 

 the sclerenchyma. The tissue on the inside of the sclerotic ring surrounding the leaf- 

 trace, and included in the area outlined by the dotted line in text fig. 3, is distinctly 

 thick walled, and farther out in the petiole may develop into sclerenchyma. No 

 sclerenchyma was observed in the stipular wings of any of the petioles contained in 

 our sections. 



The roots were all of the normal diarch type, the only tissues preserved being 

 the xylem strand and a sheath of dense sclerenchyma in immediate contact with the 

 stele. This sclerotic sheath is already present while the root is still in the inner cortex 

 of the stem, and is still maintained in the outermost parts of our sections. 



Locality. — Copper mines of Kloutschewsk, district of Bjelebei, government of 

 Orenbourg, Russia. 



Horizon. — Upper Permian, " gres cuivreux " (cf. P 2 of the Geological Table, 

 Part II., p. 219). 



General Conclusions. 



In the discussion of the vascular anatomy of the Osmundace&, Thamnopteris 

 Schlechtendalii occupies a position of special importance in that it verifies and expands 

 a number of statements that could only be made with certain reservation as regards 

 the Zalesskyas described in Part II. of this series. Of particular interest is the con- 

 firmation of the fact that the central elements of the xylem are really tracheal in 



