I2 6 NATURAL HISTORY BULLETIN. 



2. Arnulus vertical or oblique; sporangia mostly stalked. 



Sub-order IV. Polypodiace<e. 

 i. Involucre present. 1 



* Sori marginal or sub-marginal. 



■j" Involucre consisting in part or wholly of the reflexed mar- 

 gin of the frond. 

 /. Involucre single or double, the outer valve more promi- 

 nent Family I. Pteride^e. 



2. Involucre single or double, the inner valve more promi- 

 nent. Sori usually sub-marginal, linear. 



Family II. Lindsaye.e. 



■j-j" Involucre not formed by the reflexed margin of the frond. 2 



/. Involucre squamiform, sometimes fastened at the edges. 



Family III. Davallie^e. 

 2. Involucre cup-shaped or two-lipped. 



Family IV. Dicksonies. 

 ** Sori not marginal. 



■j" Sori elongated, the indusium attached along one edge. 

 i. Sori linear, sometimes interrupted, parallel and close to 

 the midrib of the frond or division. 



Family V. Blechne^:. 

 2. Sori oblique to the midrib. Family VI. Asplenies. 

 ■f"j". Sori roundish. 



/. Receptacle elevated. Mostly tree-ferns. 



Family VII. Cyathe^e. 

 2. Receptacle not elevated. Family VIII. Aspidie^e. 



ii. Involucre absent. 



"j" Sporangia scattered over entire surface of frond or divi- 

 sion. ..... Family IX. Acrostiches. 



■j-j" Sori linear, following veins, hence often pinnate or reti- 

 culated. Sporangia rarely also scattered between the 

 veins. ..... Family X. Grammitideje. 



~\W Sori linear, following veins, in sunken grooves. 



Family XI. Vittarie^e. 



|tf| Sporangia rounded.3 . Family XII. Polypodies. 



1 The genus Hemiielia of the Cyathece is without an indusium, but may 

 be recognized by the elevated receptacle on which the sporangia are 

 placed. The genus Phegopteris of the Aspidietv is also without an indusium, 

 but may be recognized by its venation, by the sori always being medial on 

 the veins, and by the stipe being continuous (not jointed) with the caudex 



8 In Endicksonia, a sub-genus of Dicksonia, the outer valve of the involucre 

 is formed by the apex of a segment, but the forms may be readily dis- 

 tinguished from the species of group f by their cup-shaped, two-valved 

 involucre enclosing nearly globular sori which terminate veins. 



3 Phegopteris and Alsophila may be sought here. See foot-note. 



