Ontogeny . 1 5 
stele. It may be that it merely represents a variant of the typica 
Leptosporangiate ontogeny, the dictyostelic condition having 
become so marked in the adult stem that it has worked back into 
the young plant and follows immediately on the protostelic condition, 
as appears to be the case in Poly podium aureuvi (Fig. 101). If we 
take that view it would be a typical instance of an ontogenetic 
history abbreviated by coenogenetic modification. On the other 
Fig. 101. Poly podium aureum. Ontogenetic evolution of dictyostely 
directly from protostely without a passage through the Lindsay a-ov solenostelic 
conditions. The leaf-traces at first single, then double (T) arise from the sides 
of the leaf-gaps, which are very long. Thus the gap just opening in F, (leaf- 
trace in H), is closed in P, and the one opening in K (leaf-trace in L, M) is not 
yet closed in T. From Chandler. 
hand it may be held that the Marattiaceae are a family which 
have never passed through the Lindsaya -phase at all, but have had 
their dictyostely evolved, so to speak, directly from protostely, the 
phloem extending round each strand independently. It is to be 
regretted that we know nothing of the ontogeny of Kaulfussia, 
which has a creeping rhizome and probably represents a more 
primitive form of adult cylinder than the other genera. The 
