25 
Flowers naked or furnished with scales. Seeds without a 
thickened covering. Foramen not hardened. 
Naiadaceal. p. 316. 
Flowers contained in a spathe. Seeds with a thick ribbed 
covering. Foramen hardened. PistiacEjE. p. 316. f 
III, e, GLUMACEOUS ENDOGENS. 
Stem hollow. Leaf sheath split. Embryo outside the albu- 
men at its base. Gramineje. p. 353. 
Stem solid. Leaf sheath not split. Embryo within the base 
of the albumen. Cyperacej 5. p. 352. 
IV, a. ACROGENS. 
Stem and leavfes not distinct. 2 
Stem and leaves distinct. 
Spores without elaters. 1 
Spores provided with elaters. 
Sporangia opening by four valves. Jungermanniaceae. 
Sporangia opening by a fissure lengthwise, collected in cone 
like heads at the summit of the stem. 
EQUISETACEiE. p. 359. 
1. — Sporangia inclosed in two or four valved sporocarps which 
are situated at the base of the leaves or leaf stalks. 
MARSILEACEAt. 
Sporangia not inclosed in sporocarps. 
Sporangia in the back or margin of the frond. 
Filices. p. 360. 
Sporangia distinct from the leaves. 
Sporangia sessile in the axil of leaves. 
LYCOPODIACEiE. p. 372. 
Sporangia borne on stalks. Musci. 
2 . — Spores with elaters. Marchantiaceae. 
Spores without elaters. Ricciace^:. 
