FILICES 



73 



apical portion, and they then assume a great variety of shapes — circular, 

 reniform, crescent-shaped, linear, or they are concealed beneath the 

 revolute margin of the leaf The sorus may or may not be covered by 

 a membrane called the indicshini, an outgrowth of the epiderm. In the 





Fig. 51. — Aspleninm AdianUim-nigrtnn L. ; rhizome with fronds sho\ving circinate 

 vernation (natural size), a, under side of fertile pinnule (magnified). 



Cyatheaceae they assume the form of a cup ; in the Hymenophyllace^e 

 they are situated at the extremity of a vein at the apex or margin of a 

 pinna. In some instances, as in our native ' flowering " or ' royal fern ' 

 (Osmunda regahs, L.), the sori completely consume, in the course of their 



