294 



FILICALES 



[CH. 



Hymenophyllaceae. (Hymenophyllum, Trichovianes.) 



The sporangia, which are attached to a columnar receptacle 

 or prolongation of a vein beyond the margin of the lamina, are 

 characterised by an obliquely transverse annulus (fig. 224, C). A 

 cup-like indusium surrounds the lower portion of the receptacle 

 which is two-lipped in Trichomanes and entire in Hymeno- 

 phyllum (fig. 270, C, D). These two filmy ferns have a wide 

 distribution both in tropical and extra-tropical regions ; they 



Fio. 229. A. Thyrsopteris elegans. B. Cyathea spinulosa. 

 C. Davallia concinna. D. Dic.ksonia coniifoUa. 



E. Alsophila excelsa. F, G. Dicksonia culcita. 



(A, after Diels and Kunze ; B, D, F, G, after Hooker ; E, after Bower.) 



are represented in the British Isles by Hymenophyllum tun- 

 hridgense, H. Wilsoni, and Trichomanes radicans. 



Cyatheaceae. (Cyathea, Hemitelia, Alsophila, Dicksonia, 

 Thyrsopteris.) 



The sporangia occur in indusiate or naked sori and have an 

 obliquely vertical and incomplete annulus (fig. 229, E). In the 

 great majority of cases the fronds are large and highly com- 



