586 FILICES.  (FERNS.) 
celled, borne on the under side of the fronds or along their margins, often 
covered by a membrane of various shape (indusium or involucre), contain- 
ing numerous exceedingly minute spores. 
Synopsis. 
SUBORDER I. POLYPODINEZ. Sporangia collected in dots, lines, 
or variously shaped clusters (sori or fruit-dots), or in indefinite masses, 
cellular-reticulated, mostly pedicelled ; the stalk running into a vertical 
incomplete elastie ring, the straightening of which ruptures the ripe 
sporangium on the inner side, discharging the spores. — Fronds simple 
or variously divided. 
Tree I. ACROSTICHE 2. — Sporangia collected in large or indefinite masses on the 
back of the frond : indusium none. 
1. ACROSTICHUM. Sporangia covering the lower surface of the upper pinnz. Veins retic- 
ulated. 
TREE I. POLYPODIEÆ. — Fruit-dots roundish, distinct, destitute of indusium, 
borne on the back of the frond. , 
2. POLYPODIUM. Fruit-dots scattered variously on the back of the frond, borne at or near 
the ends of the veins. 
Tar III. — VIT TARIEJE. — Sporangia borne in a continuous elongated marginal or 
sub-marginal furrow. 
3. VITTARIA. Fronds simple, narrowly linear. 
Tre: IV. PTERIDE 2. — Fruit-dots marginal, separate or continuous. Indusium 
formed by the reflexed margin of the frond or its lobes, opening toward the midrib. 
* Indusium thin and membranaceous, continuous around the margin of the fertile pinnæ. 
4. PTERIS. Sporangia borne on a transverse intramarginal veinlet. 
5. PELLJEA. Sporangia borne on the ends of the veins, at length confluent. 
** M ely doni; mostly formed of the reflexed ends of the lobes vio 
of the pinne or pinnules. 
6. CHEILANTHES. Sporaugia borne on the veins beneath the reflexed margin of tbe 
frond. Pinnules with a midrib. 
7. ADIANTUM. Sporangia borne on the under side of the indusium.  Midrib none or 
eccentric. 
Teme V. BLECHNEAS. — Fruit-dots dorsal, linear or oblong, borne on —— : 
veins parallel to the midrib. Indusium fixed by its outer margin, and opening s 
inner one. d» 
8. BLECHNUM. Fruit-dots linear, elongated, covered by a continuous jndusium. 
a WOODWARDIA. Fruit-dots linear-oblong, in a series near the midrib, covered «e sep- 
Tame VI. ASPLENIEÆ. —Fruit-dots dorsal, linear or oblong, oblique or at right 
angles $6 thia midrib. ee opening 
at the 
