Relation of Ptcridospenn Anatomy to that of Cycads. 5 7 
Fig. 11. — Medullosa Solmsii. A,v.typica. pv y , outer plate rings; pr 2 , inner 
plate-rings ; sr, star-rings ; It, leaf-trace. B, v. incrassata. C, v. lignosa. x' 
and x 2 , normally orientated extra vascular zones. (Adapted from Weber and 
Sterzel, 1896). 
Finally, Medullosa Leuckarti (Fig. 12) possesses a peripheral 
vascular system consisting of one or several series of plate-rings, 
each much elongated tangentially. The star-rings are rather large 
and quite concentric. 
In those cases amongst the Continental Medulloseae where the 
petioles are known, they are of the Myeloxylon type, so that the 
likeness of the petioles to those of recent Cycads noted in M. 
anglica is constant, so far as is known. 
Several other genera belonging to the family Medulloseae need 
not concern us here, Sutcliffia and the various species of Medullosa 
only, being of particular interest in a consideration of the derivation 
of Cycadean anatomy. 
As mentioned above, Worsdell is a vigorous exponent of the 
view that Cycadean anatomy has been derived from the poly- 
stelic Medulloseae, this theory having been formulated before the 
discovery of the monostelic type, Sutcliffia. It was first advanced 
by Potonid in 1899 (9, p. 168), but was stated independently and 
extended by Worsdell (23) some years later. Chodat (2, p. 38) 
more recently has supported the theory, considering the agreement 
of the Medulloseae with the Cycadaceae to be so close that he 
regards them as Protocycadeae. Scott, on the other hand, considers 
that the polystelic structure of the Medulloseae other than Sutcliffia 
(which, he says, “ does not affect the question ” (14, p. 649) ), dis¬ 
tinguishes them from the recent and Mesozoic Cycadophyta, which 
