410 BENEDICT: REVISION OF THE GENUS VITTARIA 
PLATE 20. VITTARIA WILLIAMSII Benedict 
Fic. rt. Single leaf, showing soriation and the extreme of length noted. 
Fic. 2. Whole plant (type), showing general habit, venation, me soriation. 
Fic. 3. Cross-section of half of leaf in fertile part, showing very slight depression 
where sporangia are born 
IG. 4. Chased through leaf below fertile part. 
Fic, 5. Cross-section through petiole more than 2 mm. above stem. 
IG. 6. Scale showing the very heavily thickened apical portion. 
Specimens figured: figure 1, Rusby 339, Yungas, Bolivia; 2-6, all from type 
material. 
