YASCTTLAKIA. 



421 



the basal pedicle (7v) ; in the Gleicheniees the ring is horizontal (m) ; and 

 in the Schizaece it forms a kind of cap with radiating striae on the top of 

 the spore-case (/) ; in Osmundete the ring is broad, but imperfectly de- 

 veloped (n), while in Marattiese and Ophioglossese (o) it is absent alto- 

 gether. 



In most of the tribes the spore-cases are distinct from one another, but 

 collected in groups (son) of various forms, round, linear, &c. (tig. 495, 

 6, c), on the lower surface of ordinary leaves, or of leaves especially 



Fig. 495. 



Organization of Ferns: a, plant of Polypodium vulgare; I, fragment of a pinna with 

 naked sori ; c, vertical section through one of the sori, showing the attachment of the 

 sporanges to the leaf; d, portion of a pinnule of Lastrcea Filix-mas, the sori covered 

 with indusia; e, vertical section through a sorus of the same, showing the attachment 

 of the indusium and sporanges; f, vertical section of a cup -shaped indusium and sorus 

 of Cyathea; g, marginal sorus of Hymenophyllum; h, the sime, with one valve removed, 

 to show the 'attachment of the sporanges; i, spprange of Polypodium, bursting; k, 

 sporange of Hymenophyllum ; I, sporange of Schizcea ; m, group of sporanges of Mer- 

 tensia ; n, sporange of Osmunda ; o, portion of the fertile lobe of the frond of Botrychium 

 Lunaria, with the sporanges burst ; p, spores of Ferns. 



devoted to the fructification and modified in form and texture. The sori 

 are either naked (b, c), or covered by a membranous cover or indusium 

 (d, e), the forms and modes of attachment of which furnish systematic 

 characters. In the Marattiese the spore-cases are usually more or less 

 coherent together, so as to form a false compound multilocular sporange. 

 Luerssen states that the sporangia of Marattiacese originate from a group 

 of cells and not from a single cell (trichome) as in other Ferns. In the 



