Tribe IV. Gen. XVIII— XXVII. 
§. Allantodia. Involucre membranous, arched, both margins 
attached to the vein. Species 9. 
Gen. XVIII. Doodia. Sori short, linear or crescent-shaped 
on the back of the frond and forming a row on each side of the 
costa and parallel to it. Involucre linear, opening towards the 
costa and parallel to it, placed on an arching veinlet that joins two 
veins. 1 Species. 
Gen. XIX. Polystichum. Sori placed on the middle of the 
veins at the back of the frond. Involucre circular, attached by its 
centre to the sorus, its edges free all round. 4 Species. 
Gen. XX. Neplirodium. Distinguished from Polystichum by 
its involucre being kidney-shaped and attached by the sinus. 
5 Species. 
Gen. XXI. Nephrolepis. Veins forked, very close, sunk in 
the frond, terminating at some distance from the margin, ai 
large joint, twice forked, the upper and shorter joint 
terminating in a sorus. Involucre kidney-shaped. 1 Species. 
Sub-Tribe C. 
Gen. XXII. Goniopteris. Sori round, naked and numerous, 
placed on the middle of each veinlet ; veinlets in each lobe free, 
but those nearest the costa meet those of the next lobe at an angle, 
1 Species. 
Gen. XXIII. Polypodium. Sori round, naked, placed on 
the middle of a veinlet ; veins forked and free, never uniting again 
as in Goniopteris. 3 Species. 
Gen. XXIV. Phymatodes. Distinguished by the large, 
naked sori, partly sunk in the frond, and the anastomosing veins 
2 Species. 
Gen. XXV. Dictymia. May be recognized by the simple f 
frond which is so thick as to conceal the veins, and by the large.' s 
naked sori which are often oval rather than round. 1 Species. 
Gen. XXVI. Arthropteris. Veins forked, free ; veinlets ^ 
terminating within the margin ; small, circular, naked sori at the 
end of the veinlet, forming a single series all round the pinnae 
nearer the margin than the costa. 1 Species. 
Gen. XXVII. Niphobolus. May at once be known by the thick ^ 
white scales, covering its under surface and giving it an almosl 
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