tort] SINNOTT—FOLIAR BUNDLE 265 
The mesozoic Cycadophyta, exemplified by the two genera 
Cycadeoidea and Bennettites, though showing in their cauline central 
cylinders the endarch condition characteristic of modern cycads 
and other gymnosperms, still possess primitive features in their 
leaves. The foliar trace as it departs from the stele is a single 
arched bundle. In the base of the petiole of Cycadeoidea, as 
observed by WIELAND (13), and of Bennettites Gibsonianus, as 
observed by SEWARD (8), there is a considerable amount of pri- 
mary centripetal wood and of radially arranged secondary centrif- 
ugal wood, with protoxylem between the two. The seriation of 
the protoxylem is impossible to make out, but it was doubtless 
exarch, as in modern cycads. The centrifugal wood apparently 
diminished in amount in the upper part of the petiole. The struc- 
ture of fhe vascular bundle in the lamina of the leaf is described by 
WIELAND in Cycadeoidea as “mesarch” and very similar to that in 
living cycads. ; 
Certain recent discoveries by Miss Stopes and Fuy are of 
importance in this connection. The leaf blade of V ipono phyllum, 
as described by these authors from the Cretaceous of Japan (11), 
is parallel veined and possesses collateral exarch vascular bundles 
with no centrifugal wood, thus presenting a very close resemblance 
to certain of the more simple types of leaf among the palaeozoic 
Cordaitales. 
In Nilssonia orientalis, another Japanese cretaceous form 
described by Miss Stopes (10), the leaf blade is pinnate, having a 
strong midrib from which come off parallel lateral veins. The 
vascular strands here also seem to be clearly exarch, with no trace 
of centrifugal wood. The structure of the stele and of the leaf 
trace in neither of these forms is known. 
The living Cycadales show a close resemblance anatomically 
to the palaeozoic Cycadoxyleae, notably Ptychoxylon. The central 
cylinder of the stem is always endarch with no centripetal xylem, 
Save for a few scattered tracheids, not connected with protoxylem, 
in the reproductive axes of certain species. The leaf trace departs 
as a double bundle, the halves of which soon separate and pass 
around the stem in opposite directions before entering the base 
of the leaf, where they divide into a many-bundled arch. Very 
