INTRODUCTION， 51 
16. Hymenophyllum.—Receptacles included within two-valved 
involucres of the same texture as the frond. 
** SPORE-CASES TWO-VALVED. 
TRIBE 111. — Osmundinese. — Fructification marginal paniculate ; spore- 
cases two-valved, opening at top; ring rudimentary near the apex, 
consisting of a few parallel stric. 
17. Osmunda.—Fructification forming irregular, densely-branched 
panicles on contracted rachiform segments, at the apex of 
the fronds. 
NATURAL ORDER OPHIOGLOSSACEA, OR ADDER’s ToNGUE 
FERNS. 
The Ferns belonging to this Order have their fronds plicate or 
simply folded in vernation ; their fructification being paniculate or 
spicate ; and their two-valved spore-cases without an elastic ring. 
* FRUCTIFICATION PANICULATE. 
18. Botrychium. —Spore-cases arranged in irregularly-branched 
panicles terminating a separate rachiform branch of frond. 
** FRUCTIFICATION SPICATE, 
19. Ophioglossum. — Spore-cases forming two-ranked simple 
spikes terminating a separate rachiform branch of frond. 

