tbe sporangia burst discharging numerous spores. Prothallus 

 iibove ground, green, monoecious or dioecious, on the under 

 surface of which are developed the antheridia and archegonia. 



Suborder I. POLYPOD I ACE AE. 



Sporangia in lines, dots, or clusters on the back or margin of 

 the frond or its divisions, naked or covered by a thin membrane 

 called the indusium formed from modified epidermis. 



Tribe I, Polypodieae. Frait dots round on the back or 

 ends of the veins. Indusium wanting. Stipes articulated to 

 the rootstock. Veins free. 



1. PoLYPODiUM. Fruit dots large, round, at the ends of 

 free veinlets, usually in a single row on each side of the midrib. 



Tribe IL Pterideae. Fruit dots usually marginal. Indu- 

 suim general and often partly formed from unchanged reflexed 

 margin of the frond. Veins free. Stipes continuous with the 

 rootstock. 



.2. Pteris. Sporangia a continuous marginal line, connect- 

 ing the apices of free veins. Indusium delicate, whitish, formed 

 from reflexed margin of the frond. 



3. AKdiantum. Sporangia separate, marginal, at the ends of 

 free veins. Stipes shining, black. 



4. Pellaea, Sori continuous, near the margin and near the 

 ends of free veins. Induisium continuous, membranaceous. 



5. Cheilanthes. Sori small, at the ends of the veins. 

 Fronds chaffy or woolly. Indusium continuous or interrupted. 



Tribe III. Asplenieae. Sori usually elongated, oblique to 

 the midvein, on one or both sides of the veins. Indusium at- 

 tached to the vein on one side and free on the other. Stipes con- 

 tinuous with the rootstock. 



6. Campxosorus. Sori oblong, single or in pairs, somewhat 

 curved. Veins reticulated. 



7. AsPLENiUM. Sori usually on the upper side of a veinlet. 

 Veins free. 



Tribe IV. Aspideae. Sori dorsal, round or roundish, on 



