310 



SPORANGIA OF FILICALES 



tain cells of the cortex and pith often become modified into 

 strengthening cells of stereome (Fig. 221, st). Roots arise near 

 the base of the leaves, and in some of the tree ferns form a thick 



Fig. 223. Section of a leaf of Woodwardia, showing two sori: i, indusium; 

 sp, sporangia arising from the epidermis and in various stages of develop- 

 ment. Note the epidermis, stoma, 5, palisade and spongy chlorenchyma, 

 and vascular bundles, as in higher plants. 



mat-like covering on the stems. They originate from the endo- 

 dermis of the bundles and possess a root cap and radial arrange- 

 ment of the vascular bundles as in higher plants.. 



Fig. 224. Character of sporangia: A, simple type of sporangium of 

 Osmunda with rudimentary annulus, an, of a few thickened cells. B, com- 

 mon type of sporangium — an, annulus; /, lip cells. 



(a) Structure and Character of the Sporangia. — The sporangia, 

 instead of being produced in the tissues of special branches as 

 in Ophliogossiim, are borne in curiously constructed capsules, 

 usually situated on the under surface of the ordinary green 



