58G FILICES. (FERNS.'i 



celled, borne on the under side of the fronds or along their margins, often 

 covered by a membrane of various shape (indusmm or involucre)^ contain- 

 ing numerous exceedingly minute spores. 



Synopsis* 



Suborder I. POLYPODINE^. 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 elastic ring, the straightening of which ruptures the ripe 

 sporangium on the inner side, discharging the spores. — Fronds simple 

 or variously divided. 



Tribe I. ACROSTICHK^. — 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 pinnfls< Veins retic- 



ulated. 



Tribe II. POLYPODIKiB. — Fruit-dots roundish, distinct, destitute of indusiujn, 



borne on the back of the frond. 



2. POLYPODIOM. Fruit-dots scattered variously on the back of the frond, borne at or near 



the ends of the veins. 



Tribe III. — VITTARIE-ffi. — Sporangia borne in a continuous elongated marginal or 

 sub-marginal furrow. 



3. VITTARIA. Fronds simple, narrowly linear. 



Tribe IV. PTKRIDG^. — Fruit-dota 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 pinnsB. 



4. PTHRIS. Sporangia borne on a transverse intramarginal veinlet. 



6. PELL^A. Sporangia borne on the ends of the veins, at length confluent. 



* « Indusium rarely continuous, mostly formed of the reflexed ends of the lobes or divisions 

 of the pinnae or pinnules. 



6. CHETLANTHES. Sporangia borne on the veins beneath the reflexed margin of the 



frond. Pinnules with a midrib. 



7. ADIANTUM. Sporangia borne on the under side of the indusium. Midrib none or 



eccentric. 



Tribe V. BliECHXE^. — Fruit-dots dorsal, linear or oblong, borne on transverse 

 veins parallel to the midrib. Indusium fixed by its outer margin, and opening at the 

 inner one. 



8. BLECHNUM. Fruit-dota linear, elongated, covered by a continuous indusium. 



9. WOOPWAIIDIA Fruit-dots liuear-oblong, in a series near the midrib, covered by sep- 



arate indusla. 



Tbibb VI. ASPLENIE^. —Fruit-dots dorsal, linear or oblong, oblique or at right 

 angles to the midrib. Indusium fixed by one margin to the veinlet, opening at the 

 other. 



10. CAMPTOSORUS. Fruit-dota straight or curved, scattered irregularly on the more or less 



reticulated veins, or facing each other in pairs. Frond simple. 



11. ASPLENIUM. Fruit-dots oblique, on the upper side of the veins, rarely on both sides of 



them. Vfcins free. 



