to that of the northern JD. alata, which however differs essen- 
tially in the evolution and structure of the membrane, not to 
mention the obvious character of the denticulate and crisped 
margin of our plant. There is perhaps a nearer affinity with 
D. crispatula, which differs in substance, in the perfectly entire 
margin, and in the structure of the midrib. 
I found very few specimens at Rottnest, and not having re- 
ceived any from my indefatigable correspondent in Western 
Australia, I take it for granted that this is one of the rarer 
species of the genus. ‘The cystocarpic fruit has still to be dis- 
covered. 
Fig. 1. DELESSERIA DENTICULATA,—the natural size. 2. A fruit-leaf, bearing 
a sorus of tetraspores. 3. Section of the membrane of the frond, and semi- 
section of the midrib. 4. Frustule, showing the surface-cells and the 
toothed margin :—all magnified. ° 
