PROTOPITYEAE 495 



derived from a Lower Carboniferous or possibly 

 Devonian horizon at Falkenberg, in Silesia. 1 



The stem attained a great thickness ; one of the 

 specimens was almost a foot and a half in diameter. 

 The greater part of this thickness is made up of the 

 secondary wood, which has the general structure of 

 Cordaitean or Coniferous wood, consisting of tracheides 

 and small medullary rays, the latter usually one or two 

 cells in thickness, and from one to eight or ten cells in 

 height. The bordered pits, however, which are limited 

 to the radial walls of the tracheides, are transversely 

 elongated, and are thus intermediate between the 

 scalariform type and the usual Pteridospermous or 

 Gymnospermous form of pit. The secondary bast is 

 preserved in some cases, and proves to have consisted 

 of alternating zones of sieve-tubes and stone-cells. The 

 primary part of the structure is in striking contrast 

 with that of the secondary region. The middle of the 

 stem is occupied by a large elliptical pith, surrounded 

 by a zone of primary wood, of very unequal thickness, 

 but continuous, and not broken up into distinct bundles. 

 On the sides of the ellipse, the primary xylem thins out 

 to a width of from one to three elements only, but at 

 the ends it is greatly thickened, and, in this part, xylem- 

 parenchyma is intermixed with the scalariform primary 

 tracheides. It was from the ends of the elliptical stele, 

 that the bundles passed out to the distichously arranged 

 leaves. The leaf-traces were of large size, and forked 

 immediately on becoming free from the xylem-ring. 

 The gap, left in the latter by the departure of the leaf- 

 trace, was gradually filled by the enlargement and 

 1 Solms-Laubach, Botanische Zeitung, 1893, p. 197. 



