48 
Twenty-fourth class. 
5. Ls small (5—10 *), numerous, undiv., covering the, 
gen. dichotomous, stem entirely. Sporangia in the axils 
of ordinary, or more often, reduced Is (bracts), arranged 
in a spike ....... . O 
— Ls (fronds) larger (more than 10 mm). Filices . 7 
6. Sporangia of 2 forms, the one with large spores, the 
other with numerous small ones. (Delicate moss-like pis) 
Selaginella. 677. 
— Sporangia all of one kind, with numerous small spores 
Lycopodium. 678. 
7. Sporangia arranged in a spike or panicle . . 8 
— Sporangia grouped in brown clusters (sori) on the under 
side of the frond ....... 10 
8. Fronds rolled up spirally when young, the upper part 
of one frond fertile, forming a panicle Osmunda. 682. 
— Fronds not rolled up when young, divided more or less 
deeply into a fertile and a barren part . . ,9 
9. Fructification in a distichous spike. Barren part of the 
frond undiv.Ophioglossum. 680. 
— Fructification in the form of a panicle (rarely reduced 
to a spike). Barren part of the frond pinnatisect or 
2-pinnatisect (very rarely entire) Botrychium. 681. 
10 (7). Fertile and barren fronds differing in form . 11 
— Fertile and barren fronds of the same form . 13 
11. Groups of sporangia forming 2 lines, parallel to the 
middle nerve.Blechnum. 688. 
— Groups of sporangia, at any rate finally, forming a con¬ 
tinuous marginal line ...... 12 
12. Fronds 3-pinnatisect .... Allosurus. 685. 
•— Fronds simply pinnatisect; segments of the barren fronds 
finely toothed ...... Pteris. 687. 
— Fronds pinnatisect; segments of the barren fronds pin- 
natifid ... .... Onoclea. 696. 
13 (10). Fronds thickly covered on the under side with 
chaffy scales (tegument 0) .... 14 
— Fronds glabr. underneath, or with scattered chaffy scales 
15 
14. Fronds simply pinnatisect . . . Ceterach. 692. 
— Fronds 2-pinnatisect . . . Gymnogramme. 684. 
15. Groups of sporangia covered entirely or partly by the 
reflexed edge of the frond ..... 10 
— Groups of sporangia covered, at any rate when young, 
by a membranous tegument (indusium) . . 17 
— Groups of sporangia naked, without a tegument, and 
not covered by the edges of the frond . . 22 
16. Groups of sporangia in a continuous line. Pis of 70 to 
150 cm .Pteris. 687. 
