Explanation of Plate IV. 



Pteris biaurita L. p. 136. 



Fig. 1. Three pinnules (or lobes), showing venation of typical biaurita. 

 X 2. 



Fig. 2. Two pinnules (or lobes) of the form quadriaurita showing a 

 vein springing directly from the midrib of the pinna. X 2. 



Fig. 3. Two pinnules from the same frond as fig. 2, showing typical 

 venation of quadriaurita. X 2. 



Fig. 4. A portion of a pinna of the pentagonal form, showing the vena- 

 tion of tiemoralis. X 2. 



Fig. 5. A part of a pinna of nearly typical quadriaurita, showing a 

 broad base. X i- 



Fig. 6. A part of a pinna of the pentagonal {tiemoralis) form, showing 

 a tapering base. X i- 



Figs. 1, 2, 3, and 5 represent specimens from Ometepe, and figs. 4 and 6 

 from Castillo. 



