IX FILICINE^ LEPTOSPORANGIAT^ 311 



folded (Salviniaceae) ; sporangia without an annulus and borne 

 in special ''sporocarps," which are either modified branches of 

 ordinary leaves (Marsiliaceae) or a very highly developed 

 indusinm. 



Order II. Hydropterides. 



Family i, Marsiliaceae. 



Family 2. Salviniaceae. 



Order I. Filices 



• 



The eight families of the Filices form an evidently very 

 natural group, but there has been a good deal of disagreement 

 as to their relative positions. The Osmundacese are generally 

 recognised as approaching most nearly the eusporangiate Ferns, 

 and the Gleicheniacese come next to these. The Hymeno- 

 phyllacese are usually considered at the other extreme of the 

 series, but there are a number of reasons why this seems doubt- 

 ful, and I am inclined to assign them an intermediate position. 

 Their structure and development give evidences of their being 

 a specially modified group adapted to living in very damp 

 situations, and they probably cannot be regarded as connecting 

 any of the other families, but rather as a side branch which has 

 developed in a direction away from the type. They come near- 

 est the Gleicheniaceae and Osmundacese in the structure of the 

 sexual organs, and the sporangium shows points in common 

 with the former family. The sporangium, however, also re- 

 sembles that of the Cyatheacccne, and the strongly-developed In- 

 dusium is much like that of the latter. The SchizgeacCci^: also 

 may possibly form a side branch from the ascending serie? 

 which ends in the Polypodiacese. 



Professor Bower (19), who does not recognize the Ophio- 

 glossacege as belonging to the Filicinese, divides the other hom- 

 osporous Ferns into three suborders, based upon the develop- 

 ment of the sporangia. His first suborder, "Simplices," includes 

 the Marattiacese, Osmundacese, Schiz?eacese, Gleicheniaceae, and 

 Matoniaceae. In these families all the sporangia in a sorus are 

 developed simultaneously, and the output of spores is rela- 

 tively large. The second suborder, '"Gradatse," comprises the 

 Hymenophyllaceae (inc. Loxsomaceae) , Cyatheaceae (inc. Dick- 

 sonieae — in part), and one sub-family, Dennstaedtineae, belong- 

 ing to the Polypodiacese. In these the sporangia arise in 



