46 
N. Bancroft. 
cambium is continuous through the leaf-gaps with the normal zone, 
so that each segment of wood is surrounded by a cambium and the 
stem has a polystelic appearance. This anomaly is particularly 
interesting in connecting the Lyginopterideae with another group of 
the Lyginopteridean alliance—the Cycadoxylese. The secondary 
wood of the representative type— Cyciuloxylon robustum (15)— 
resembles that of Lyginopteris oldhamia (Fig. 4). The medullary 
rays are broad and high, and must originally have imparted to the 
wood a very soft parenchymatous texture, like that, as Scott 
Fig. 4. —Cycadoxylon robustum. Part of transverse section of stem, showing 
inner portion of normal wood, x 2 , with two inverted zones of wood and bast, 
x 3 , ph 3 and x\ ph'; p, parenchyma; mr, medullary ray. (Adapted from 
Scott, “ Studies.”) 
remarks, of a recent Cycad (14, p. 483). The tracheides bear 
multiseriate pits on their radial walls only. Strands of primary 
wood surrounding the pith —so characteristic a feature in Lygino¬ 
pteris—have not been detected with certainty in Cycadoxylon; if 
present at all, they must have been much reduced, presenting an 
approach to the endarch condition of the wood of recent Cycad 
stems. Somewhat fragmentary leaf-traces are seen, here and 
there, passing out through the secondary wood; but in these again, 
the primary xylem is not evident. It cannot therefore be definitely 
decided whether the primary structure of the wood was of the 
Lyginopteris type, or whether the vascular structures were truly 
endarch as in the stem of recent Cycads. The stem presents a 
