20 



Ring small, lateral or apical, not encircling the sporangium. 



d. Ring rudimentary or operculiform, consisting of a compact 



group or a whorl of thickened cells, apical, if apparently 



lateral, then the sporangia transversely oblong, i. e. 



attached at the side. V. Schizaeaceae. P. 109. 



d.d. Ring rudimentary or circular, lateral, the sporangia not 



transversely oblong, attached at the base. 



e. Ring rudimentary, consisting of a group of thickened 



cells only; indusium wanting. 



YIII. Osuiundaeeae. P. 755. 



e.e. Ring circular, the cells only partly thickened; 



indusium present. (IVa. Loxsomaceae). 



Ring rather large, more or less completely encircling the 



sporangium. 



1. Ring horizontal or oblique ; stomium vertical. 



* Fronds with stomata; indusium wanting; receptacle 

 dot-like. III. Olcichcnlaccae. P. 55. 



•• Fronds without stomata; indusium present; recep- 

 tacle conspicuous, elevated. 



IV. Slymenophyllaeeae. P. 65. 

 l.±. Ring vertical or obUque; stomium horizontal. 



9. Ring vertical, incomplete (rareley oblique and 

 complete, in forms with a non-arborescent stem and 

 marginal linear indusia); indusia wanting or present 

 (never marginal cup-shaped or 2-valved in forms 

 with an arborescent or subarborescent stem). 



VI. Polypofliaceae. P. 121. 

 2.2. Ring oblique, complete (rarely vertical and incomplete, 

 in forms with an arborescent or subarborescent 

 stem and cup-shaped or 2-valved indusia); indusia 

 wanting or present (never marginal linear in forms 

 with a non-arborescent stem). 

 3. Fronds pedato-flabellate or sympodially branched ; 

 indusia superior, peltate-umbellate. 



II. llatoniaceae. P. 51. 



3.3. Fronds simple or pinnately divided ; indusia 



wanting or inferior, globose, cup-shaped, 2-valved 



or scale-like. I. Cyaihcaceae. P. 9. 



