FILICES. (ferns.) 657 



Tribe IV. ASPIDIEiE. Sori round or roundish, on the back or rarely at the apex of 

 the fertile vein, provided with a special indusium, rarely naked. Stipes not articulated to 

 the rootstock. 



* Indusium obsolete or none. 



11. Pbegopteris. Sori round, rather small. Veins free in our species. 



* # Indusium evident, round or roundish, covering the sporangia, at least when young. Steril* 



and fertile fronds not very unlike. Veins free in our species. 



12. Aspidium. Indusium fiat, orbicular or round- reniform, fixed by the centre, opening all 



round the margin. 



13. Cystopteris. Indusium convex, fixed by a broad base partly under the sorus, com- 



monly reflexed as the sporangia ripen. 



* * * Indusium obscure, irregularly semicircular. Fertile fronds much contracted and very 



unlike the sterile ones. 



14. Strutliiop teris. Fertile frond simply pinnate. Sterile frond with free veins. 



15. Onoclea. Fertile frond twice pinnate. Sterile frond with reticulated veins. 



* # # # Indusium roundish or stellate, placed beneath the sporangia, sometimes enclosing them 



and then bursting open from the top. 



16. Woodsia. Indusium very delicate, cleft into irregular lobes, or divided into a ciliate 



fringe. Veins free. 



Tribe V. DAVALLIE55. Sori roundish or transversely elongated, borne at the ends 

 of the veins or on marginal cross-veinlets, with an indusium attached at the base or base 

 and sides and opening towards the margin of the segment. 



17. Dicksonia. Sori marginal, very small, the indusium cup-shaped, somewhat 2-valved, 



the under portion confluent with a lobule of the frond. Veins free. 



Suborder II. SCHIZJEACEJE. 



Sporangia ovate, sessile, having a complete transverse articulated ring 

 at the apex, and opening by a longitudinal slit. (PI. 19.) 



18. Scbizsea. Sporangia naked, fixed in a double row to the midrib of the narrow fertile 



segments. Sterile fronds rigid, simple or dichotomously branched. 



19. Lygodium. Sporangia borne in a double row on narrow fertile segments, each spo- 



rangium seated on a separate veinlet, and provided with a special scale-like indusium. 

 Fronds leafy, climbing. 



Suborder III. OSMUN5>ACE^. 



Sporangia naked, globose, mostly pedicelled, reticulated, Avith no ring or 

 mere traces of one around the apex, opening into two valves by a longitudinal 

 slit. (PI. 19.) 



20. Osmunda. Fertile pinnae or fronds very much contracted, bearing the abundant and 



large sporangia upon the margins of the very narrow segments. Veins free. 



Suborder IV. OPHIOGIX>SSACEJE. 



Sporangia spiked, destitute of a ring, naked, coriaceous and opaque,, 

 not reticulated, opening by a transverse slit into two valves, discharging 

 very copious powdery spores. Fronds straight, never rolled up in tho 

 bud! (PI. 19.) 



21. Botrychinm. Sporangia in pinnate or compound spikes, distinct. Veins free. 



22. Ophioglossum. Sporangia cohering in a simple spike. Veins reticulated. 



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