EXPLANATION OF PLATE XVII. 



PTERIS. A pinnule of P. aquilina, ami (2) a piece ( one of the lobes, 

 enlarged, the marginal indusium rolled back on one side, displaying the 

 fruit ; the sporangia all removed from the lower part to show the recep- 

 tacle that bears them, viz. a cross-line connecting the tips of the veins. 



ADIANTUM. (1) Piece of the frond of A. peclatum ; (2) a pinnule some- 

 what enlarged; and (3) a piece of one more enlarged, with the iudusium 

 of one fruit-dot turned hack to show the attachment of the fruit. 



CHEILANTHES. (1) Small plant of C. vestita; and (2) a fruit-bearing 

 pinnule, enlarged. 



WOODWAKDIA. (1) Portion of the sterile and (2) of the fertile frond of 

 W. angustifolia ; (3) a piece of the latter, enlarged ; (4) piece of the frond 

 of W. Virginica; and (5) part of a fruiting lobe, enlarged. 



