IX FILICINE^ LEPTOSPORANGIAT^ 311 



folded (Salviniacese) ; 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. Marsiliacese. 



Familv 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- 

 phyllaceae 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 Gleicheniacese and Osmundaceae 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 CyatheacCcX, and the strongly-developed in- 

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

 may possibly form a side branch from the ascending series 

 which ends in the Polypodiacese. 



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

 glossacese 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, Schizgeacese, Gleicheniacese, and 

 Matoniacese. 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 

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

 soniese — in part), and one sub- family, Dennstaedtinese, belong- 

 ing to the Polypodiaceae. In these the sporangia arise in 



