XXIX] HETERANGIUM 85 



having a 'great preponderance of fern-like characters,' but having 

 regard to the resemblance of the primary xylem of the latter to 

 that of the Osmundaceae it would seem doubtful whether in 

 their relation to the Ferns there is any important difference. 

 Heterangium may safely be spoken of as the more primitive genus. 

 The polydesmic character of the petioles of most species is parti- 

 cularly interesting as it brings the genus nearer to the Medulloseae 

 and to Rhetinangium 1 . 



1 Scott (15). 



