356 THE MICROSCOPIST. 



site or digitate at apex of leaf, set among hairs, splitting 

 longitudinally on the outside. No indusium. 



Gen. 3. Lygodium. Sporangia sessile, alternately bi- 

 seriate on marginal lobes of leaf, splitting longitudinally, 

 each veiled by a scalelike, hood-shaped indusium adhering 

 transversely to the nerves. 



Gen. 4. Mohria. Sporangia sessile in one row, close to 

 margin of leaf, splitting longitudinally on the outside. A 

 spurious indusium formed by revolute margin of leaf. 



Order 2. MA RATTIACE^. Sporanges on lower sur- 

 face, usually blended together, or very closely approxi- 

 mated. No annulus. 



Gen. 1. Angiopetris. Sporangia in two rows near apex 

 of transverse veins, distinct, forming linear sori, opening 

 by a slit on outer side. No indusium. 



Gen. 2. Kaulfussia. Sporangia on anastomoses of 

 veins, radiately connate, forming roundish sori, opening 

 by a slit at apex. 



Gen. 3. Marattia. Sporangia in two rows near apex of 

 transverse veins, connate, forming oblong sori, gaping 

 transversely by a vertical slit. Indusia connate with 

 sori. 



Gen. 4. JEupotium. Sporangia as 3, but pedicellate. 



Gen. 5. Dancea. Sporangia in two rows, near trans- 

 verse veins, connate into linear sori, opening by a pore. 

 Indusia superficial, encircling the sori. 



Order 3. OPHIOGLOSSE^E. Sporanges on lower sur- 

 face of leaf (reduced to mere ribs), never blended. No 

 annulus. 



Gen. 1. Ophioglossum. Sporanges dehiscing transversely, 

 connate on an undivided distichous spike. 



Gen. 2. Botrychium. Sporanges as last, on a distichous, 

 secund, bi-tri-pinnate spike. 



Gen. 3. Helminthostackys. Sporanges dehiscing exter- 



