;8 OUR NATIVE PERNS AND THEIR ALLIES. 



oblique to the midrib, or rarely sub-parallel with it. Indusium 

 fixed by one margin to the veinlet, opening at the other, some- 

 times double. 



* Veins free. 



XVI. Asplenium L. Sori on the upper side of a fertile 

 veinlet, rarely on both sides. 



XVII. Scolopendrium Sm. Sori linear, confluent in 

 pairs, which appear like a single sorus with the double indusium 

 opening in the middle. 



** Veins reticulate. 



XVIII. Camptosorus Link. Sori oblong or linear, 

 borne partly on veins parallel to the midrib, partly on veins 

 oblique to the midrib. 



TRIBE IX. ASPIDIE/E. Sori dorsal, round or roundish, 

 on the back or rarely on the apex of a vein. Indusium usually 

 membranous, rarely wanting. 



* Without indusia. 



XIX. Phegopteris Fee. Sori round, rather small, borne 

 oh the back of the free veins. 



** With indusia. 

 t Indusia superior. 



XX. Dryopteris Adans. Indusium orbicular and fixed by 

 the centre, or reniform and fixed by the sinus, opening all 

 round the margin. Sori mostly on the back of the veins. 



XXI. Nephrolepis Schott. Indusium reniform, fixed at 

 the sinus or at the arcuate base, opening toward the margin of 

 the frond. Sori at the end of free veins. 



tt Indusia fixed by a broad base partly under the sorus. 



XXII. Cystopteris Bernh. Indusium convex, usually 

 reflexed as the sporangia ripen. Texture delicate. 



ttt Indusia obscure. Fertile frond much contracted, very un- 

 like the sterile. 



XXIII. Onoclea L. Sori dorsal on the veins of the con- 

 tracted pinnae, concealed by their revolute margins. 



tttt Indusia inferior. 



