FILICES. 333 



SUBORDER I. POLYPODIACE^. 



Sporangia globular, or slightly flattened laterally, collected in patches, lines or 

 dots of various shapes, stalked, and provided with a vertical incomplete many- 

 jointed ring, which straightens at maturity and discharges the very minute 

 spores. 



TRIBE I. POLYPODIE/E. Sori round or oblong, placed on the veins or at the ends of the 

 veins, destitute of indusiura. Stalk articulated to a slightly prominent knob of the usually 

 elongated creeping rootstock. Veins free or variously reticulated. 



1. Polypodium. (Character of the tribe, of which it is the only genus.) 



TRIBE II. GRAMMITIDE^E. Sori more or less elongated, without indusium, placed on the 

 back of the frond or its divisions, and usually following the veins, or only at the tips of the 

 latter and near the margin of the frond. Fronds often scaly or tomentose, or covered be- 

 neath with colored powder. 



2. Gymnogramme. Sori much elongated, following the veins, and like them often branched 



or reticulated. 



3. Notholeena. Sori but little elongated, often of very few sporangia, placed below the tips of 



the veins near the margin of the lobes of the frond. 



TRIBE III. PTERIDE^E. Sori close to the margin of the frond or its divisions, sometimes 

 extending down the veins, covered, at least when young, by an involucre opening inward 

 and either consisting of the margin or produced from it. 



4. Cheilanthes. Sori minute, at the ends of the unconnected veins, covered by a usually inter- 



rupted involucre. Small ferns, often woolly, chaffy or pulverulent. 



5. Pellaea. Sori near the ends of the veins, often confluent. Involucre membranaceous, contin- 



uous round the pinnules. Sterile and fertile fronds much alike and smooth ; the stalk 

 dark-colored. 



6. Cryptogramme. Sori extending down the free veins. Involucre very broad, at length flat- 



tened out and exposing the now confluent soil. Sterile and fertile fronds unlike, smooth ; 

 the stalk light-colored. 



7. Pteris. Sporangia borne on a continuous vein-like marginal receptacle, which connects the 



ends of the veins. Involucre continuous round the pinnules. Stalk light-colored. 



8. Adiantum. Sporangia borne at the ends of the veins, on the under side of the reflexed mar- 



gin of the frond. Midvein of the pinnules mostly eccentric or dissipated into forking 

 veinlets. Stalk dark-colored. 



TRIBE IV. BLECHNE^E. Sori more or less elongated, borne on a fruiting veinlet or a 

 special receptacle parallel to the midrib, either near it or remote from it, and provided with 

 a special usually concave or arched indusium attached to the receptacle outside the sorus 

 and opening along the inner edge. 



9. Lomaria. Sori continuous from the base of the pinna to its apex, the receptacle nearer the 



margin than the midvein. Fronds in our species once pinnate, the fertile ones with 

 contracted pinnae. 



10. Woodwardia. Sori interrupted, forming a chain-like row each side of the midvein. 



Fronds in our species ample, compound ; the veins reticulated. 



TRIBE V. ASPLEN1EJE. Sori more or less elongated, borne on veins oblique to the mid- 

 vein, covered by a special usually flattened indusium attached to the fertile veinlet by one 

 edge and free on the other. 



11. Asplenium. Sori on the upper side of the fertile veinlet, less commonly on both sides of it. 



Veins free in our species. 



TRIBE VI. ASPIDIE^E. Sori round or roundish, on the back or sometimes at the tip of the 

 fertile veinlets, naked or provided with a special indusium. Stalk not articulated to the 

 rootstock, the tropical genus Oleandra excepted. 



12. Phegopteris. Sori dot-like, minute, borne on the back of the fruiting veinlets ; indusium 



none. 



13. Aspidium. Sori round, borne on the back or at the apex of the veinlets ; indusium orbicu- 



lar or else round-reniform. Mostly large ferns. 



14. Cystopteris. Indusium convex, delicate, "lixed across the back of the veinlet by a broad 



base, usually turned back by the ripening sporangia. Delicate ferns with small 

 fronds. 



15. Woodsia. Indusium placed beneath the sorus, and partly or wholly enclosing it, divided 



into irregular lobes or into a delicate fringe. Fronds small. 



