Twenty-fourth class. 
49 
— Groups of sporangia in an interrupted line. Pis of 
20—30 cm .Adiantum. 686. 
17. Groups of sporangia lateral, linear or elongated, rarely 
horse-slioe shaped. Tegument with a broad base, united 
laterally to the nerve ...... IS 
— Groups of sporangia dorsal (sup. or inf.), gen. rounded, 
inserted on the back of the nerve . . . 20 
18. Groups of sporangia in pairs, their teguments turned 
with their free edges one towards the other. Fronds undiv. 
Scolopendrium. 689. 
— Groups of sporangia isolated. Fronds more or less divided 
19 
19. Groups of sporangia linear or longish. Chaffy scales 
arranged like lattice-work . . . Asplenium. 690. 
— Groups of sporangia oblong or horse-shoe shaped. Scales 
not latticed.Athyrium. 691. 
20 (17). Tegument sup. (lying on the group of sporangia), 
or peltate, i. e. attached in the centre, or reniform and 
attached in the indenture . . . Aspidium. 694. 
— Teg. inf. (springing from the base of the group of spor¬ 
angia) ......... 21 
21. Teg. unilateral, only spread over the groups of spor¬ 
angia from one side, and finally folding back 
Cystopteris. 695. 
— Teg- completely surrounding the groups of sporangia, 
cut like a fringe ..... Wooclsia. 697 
22 (15). Petiole jointed at the base. Fronds simply pinnatisect 
Polypodium. 683. 
— Petiole not jointed. Fronds 2—3-pinnatisect 
Phegopteris. 693. 
