344 SYSTEMATIC ARRANGEMENT. PART n. 



which agrees in its general features with that of most 

 modern observers. 



The two leading groups are the Annulate and the 

 Exannulate Ferns, the first being much the larger divi- 

 sion, and consisting of the order Polypodiacese, which 

 comprises the True Ferns, while the second includes 

 the two orders Marattiacese and Ophioglossacese, which 

 are some times called Pseudo- Ferns. 



The POLYPODIACE^E, distinguished by the ring or an- 

 nulus, which more or less completely girts the sporangia, 

 offer so much variety of structure that it becomes neces- 

 sary to subdivide them ; and for this purpose characters 

 derived from the form, number, or position of the sporan- 

 gia, or the structure or development of the ring, are 

 chiefly relied on. This gives several groups, e.g. Poly- 

 podinese, the most comprehensive of all, including some 

 ten or twelve minor groups, in which the sporangia are 

 almost equally convex, and have a vertical and nearly 

 complete ring, and in which the dehiscence is trans- 

 verse at a part called the stoma, where the striae of the 

 ring are elongated, and apparently weaker ; Cyatheinese, 

 in which the spore-cases are sessile or nearly so, seated 

 on an elevated receptacle, with the nearly complete 

 ring more 'or less obliquely vertical, that is, vertical 

 below, curving laterally towards the top, and the de- 

 hiscence transverse ; Matoninese, a single species only, 

 in which the sporangia are sessile, bursting horizon- 

 tally, not vertically, the ring being broad, suboblique, 

 and nearly complete, and the dorsal sori oligocarpous, 

 covered by umbonato-hemispherical indusia, affixed by 

 a central stalk ; Gleicheninese, with the ring complete, 

 transverse, either truly or obliquely horizontal, the spo- 

 rangia globose-pyriform, forming oligocarpous sori, i.e. 

 sori consisting of but few spore-cases (two or four to ten 

 or twelve), situated at the back of the frond, sessile or 

 nearly so, and bursting vertically, the fronds, moreover, 



