6j6 Marsh . — The Anatomy of some Xerophilous Species of 
to dictyostely, viz. by overlapping of leaf-gaps formed in two rows on the 
dorsal surface. The P. andromedaefolia which I examined may perhaps 
have been older material than that used by Gwynne-Vaughan, for though 
P ig. 6. Pellaea andromedaefolia. Series of sections of stem in acropetal order. 
it showed a dorsiventral dictyostele, its structure was more complicated 
than that which he describes. The leaves come off at approximately the 
same level in threes or in pairs (Fig. 6). From the appearance of section 29 
in my series it seems that the arrangement in threes may be produced by 
