Q2 BOTANICAL GAZETTE [FEBRUARY 
it connects at the anterior end of the leaf'gap. In M. alata it 
joins the external system in the internodes, is freest at the nodes, 
and is concerned with the closing of the leaf gap. In the solenostelic 
ferns roots are not connected with the internal system as they are 
in the Marattiaceae. In such solenostelic ferns as have more than 
one concentric cylinder in the medullary system, as in Matonia, the 
Fic. 3.—View from the upper side of a model, showing the origin of a medullary 
cylinder from the anastomosis and branching of two medullary strands. 
formation of the second cylinder is markedly different from that in 
Marattia. -In the Cyatheaceae the medullary strand takes part in 
the formation of several leaf traces, in Matonia it is a definite part 
of a single trace. In Maraittia it shares in forming the region from 
which a leaf trace goes off. 
If the medullary system of Marattiaceae is homologous with that 
of the Dicksonieae, Cyatheaceae, and Polypodiaceae, modifica- 
tions must have taken place in the Marattiaceae. The place of 
