FERN TYPES. 



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looped, curved, or marginal, and only the ternary one netted {D. composifa). The 

 secondary and ternary veins are remarkably shortened in the former^ and scarcely, or 

 not distinctly, separated from each other. The meshes of the network enclose free 

 venules or not, and are accordingly D. appendiculata or D. exappendiculata {Chrysodium 

 Lanzaanum). 



"Finally, there are the PIdebodium (fig. 9) and Drynaria (fig. 10) types of venation 

 belonging to the group with anastomosing veins. In the former the very much abbreviated 

 secondary veins form, by a peculiar anastomosis of their forked branches, a prominent row of 

 larger long meshes on each side of the midrib, and several rows of loops. In the Drynaria 

 type the anastomosing ternary veins are given off" in a pinnate manner from both sides of 



Fig. 9. — Phlebodiura. 



Fig. 10. — Drynaria. 



the elongated secondary ones, which are strongly curved or looped. The rays or appendao-es 

 within the ternary meshes anastomose in such a manner as to form a network resembliu"- 

 the venation of dicotyledonous leaves. The meshes usually enclose free venules. When 

 the ternary segments are regularly rhomboid or elongated, it is the Drynaria reyularis 

 type ; when these segments are indistinctly outlined and of irregular shape, they belono- 

 to the D. irreyularis type {Glossocldamys transmutans, PI. Ill, fig. 3), and when the 

 secondary veins form neither curves nor loops, but terminate in the margin, combining 

 with the marginal ones, they compose the Drynaria composita type, a type at present 

 confined to the fossil genus Meniphjllum." 



4 



