FILICES. (FERNS.) 679 



Tribe V. ASPLENIE^E. Sori more or less elongated, occupying one or both sides ol 

 oblique veins, covered by a special indusium which is attached by one side to the fertile 

 vein, and is free on the other. Stipes not articulated. 



9. Asplenium. Sori on the upper side or rarely on both sides of a veinlet. Veins fre 

 in all our species. 



10. Scolopendrium. Sori linear, confluent in pairs, each pair appearing like a single 



sorus with a double indusiuni opening down the middle. Veins free. 



11. Camptosorus. Sori oblong, variously curved, or some of them in opposite pairs. 



Veins reticulated. 



Tribe VI. ASPIDIE2E. Sori round or roundish, on the back or rarely at the apex of 

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

 * Indusium obsolete or none. 



12. Phegopteris* Sori round, rather small. Veins free in our species. 



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



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



13. Aspidium. Indusium flat or slightly convex, orbicular or round-reniform, fixed by 



the centre, opening all round the margin. 



14. 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. 



15. On odea. Sporangia on an elevated receptacle ; divisions of the fertile frond pod-like 



or berry-like. 



Tribe VII. WOODSIE^E. Sori round, borne on the veins ; indusium fixed under the 

 sorus, divided into segments or into slender filaments. 



16. Woodsia. Small ferns with free veins. Indusium very delicate. 



Tribe VIII. DICKSONIE^E. Sori roundish, marginal or submarginal. Indusium 

 cup-shaped or two-valved, the outer portion composed of a reflexed lobule of the frond, 

 or more or less united to it. 



17. Dicksonia. Indusium in our species small, membranaceous, nearly globular. Frond 



elongated, decompound. 



SUBORDER II. Hymenophyllacese. Sporangia sessile on a 

 bristle-like receptacle within a cup-shaped or bivalvular involucre, the 

 ring transverse and complete. Fronds delicately membranaceous. 



18. Tricliomaiies. Involucres funnel-form or cup-shaped. 



SUBORDER III. Schizseaceae. Sporangia ovate, sessile, having a 

 complete transverse articulated ring at the apex, and opening by a longi- 

 tudinal slit. (PL 19.) 



19. Schizaea. Sporangia naked, fixed in a double row to the midrib of the narrow fertile 



segments. Sterile fronds rigid, simple or dichotomously branched. 



20. 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 IV. Osmundacese. Sporangia naked, globose, mostly 

 pedicelled, reticulated, with no ring or mere traces of one near the apex, 

 opening into two valves by a longitudinal slit. Stipes winged at base 

 and almost stipulate! (PL 19.) 



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



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



