58G FiLicES. (ferns.) 



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

 covered by a membrane of various shape (indushaii or involucre), contain- 

 ing numerous exceedingly minute spores. 



Synopsis. 



Suborder I. POLYPODINEiE. Sporangia collected in dots, lines, 

 or variously shajied clusters (son' or fru it-dot. i), 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. ACROSTICHE^. — Sporangia collected in large or indefinite masses on the 

 back of the frond : indusium none. 



1. ACROSTICIIUM. Sporangia covering the lower surface of the upper pinnse. Veins retic- 



ulated. 



Tribe II. P01iYP0DIE.aE. — Fruit-dots roundish, distinct, destitute of indusium, 

 borne on the back of the frond. 



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



the ends of the veins. 



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

 sub-marginal furrow. 



3. VITTARIA. Fronds simple, narrowly linear. 



Tribe IV. PTERIDE^Si. — Fruit-dots marginal, separate or continuous. Indusium 



formed by the rcflexed margin of the frond or its lobes, opening toward the midrib. 

 • Indusium thin and membranaceous, continuous around the margin of the fertile pinnae. 



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



5. PELLvEA. 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. CHEILANTIIES. Sporanpa borne on the veins beneath the reflexed margin of the 



frond. Pinnules with a midrib. 



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



eccentric. 



Tribe V. BIjECHNE.^. — 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. BLECIINUM. Fruit-dots linear, elongated, covered by a continuous indusium. 



9. \VOOI)\VAIU)IA truit-dots linear-oblong, in a series near the midrib, covered by sep- 



arate indusia. 



Tribe VI. A SPI,F1VIEjE. —Fruit-dots dorsal, linear or oblong, obliq\io or nt right 

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

 other. 



10. CAMPTOSOnU.S. Frultdots straight or curved, scnttfred irregularly on the more or lesK 



rotioulat<'(I veins, or firing enoli other in pairs. Frond simple. 



11. ASITiE.N'IUM. Fruit-dota obliii'ie, ou the upper side of the veius, rarely un both sides of 



tbeui. A'l'init free. 



