ASPIDIUM. 23 



Sporangia usually medial, rarely terminal. 

 Sori circular. 



Indusium orbicular and central, seldom eccentric and reniform. 

 Fronds simple, pinnate, or bi-tripinnate; the serrate edges 

 of the frond rigidly spinulose. 



Distinguished from Lastrea by the rigid spinulose habit. 



Aspidium, Sageiiia, Cyrtomium, Nephrodium, Lastrea, and 

 Polystichum run into each other so closely, that it seems 

 advisable to follow Kunze in calling them mere sections of 

 one genus. Were I to separate any of them, it would be 

 done with regard to the habit of the plant alone, and in this 

 case I would place Cyrtomium among the Polysti chums. In 

 the most restricted form of Aspidium the habit and general 

 appearance is also distinct from Lastrea, still I have adopted 

 the views of Kunze and retained it. 



OnocMea, with its two forms of fronds; Fadyenia, with its 

 two forms of fronds and proliferous habit; Woodsia, a group 

 of small slender Ferns, with peculiar indusium. The genus 

 Cystopteris, another group of small delicate Ferns; Didymoch- 

 Icena, with its several very distinct characters, hereafter to be 

 mentioned; Neplirolepis , with its distinct habit, and having the 

 petiole articulated with the rachis, giving it a power of throwing 

 off its pinnae freely; and Oleandra; are all to me sufficiently 

 distinct to keep them separated from the genus Aspidium. 



We have British examples of both Lastrea and Polystichum. 



In Lastrea we have: — 



Cristata Oreopteris Thelypteris 



Filix-mas Eigida Multiflora 



E-ecurva Spinulosa Dilatata 



In Polystichum we have: — 



Aculeatum Angulare Lonchitis 



Aspidium jilix-mas, A. aculeatum, and A. angulare vary so 

 much from spores, that it is difficult to recognize the departure 

 from the normal form as mere varieties; however these will be 

 more closely spoken of when describing the species. 



