FILICES 



89 



The sessile or shortly stalked, roundish, but unsymmetrical sporanges 

 are not strictly epidermal in their origin. They bear on one side of their 

 apex a modified annulus in the form of a group of cells of peculiar form, 

 and dehisce vertically on the other side. Todea (Willd.) presents no 



difference between the fertile 

 and sterile leaves ; while in 

 Osmunda (L.)the fructification 

 has the appearance of a con- 

 tinuous or interrupted panicle, 



FIG. 67. Mucilage-gland from Osmitnda. 

 regalis (magnified). (After Gardiner.) 



from the entire absorption of 

 the mesophyll of the fertile 

 part of the leaf. In some 

 species of Todea the leaf con- 

 sists of only a single layer of 

 cells. In Osmunda there are 



FIG. 68. Sporange of Osiminda 

 (magnified). 



abundant mucilage-cells at 

 the base of the leaf-stalk. 

 The ^vascular ' bundles of the 

 stem are collateral, as con- 

 trasted with the concentric 

 bundles of typical ferns, and their course bears more resemblance to 

 that in Gymnosperms and in Dicotyledons. In the structure of the 

 leaves, and in the structure and development of the growing point, 

 Osmundaceae exhibit a transitional condition between the typical ferns 



FIG. 66. Osmunda regalis L. Portion of frond 

 (natural size). 



