562 MINNESOTA BOTANICAL STUDIES. 



and more robust stipe. It differs from A. angusta especially in 

 the form of the sporophylls." 



EXPLANATION OF PLATE XXXIII. 



Figure i. Mature plant reduced y z ; a, b, c, d, young plants, 

 showing different stages of development. 



Figure 2. Cross section of sporophylls, X 400. 

 Figure 3. Section of midrib, x 2. 



