EXPLANATION OF PLATE XVII. 



PTERIS. — A piuiiule of P. aquilina, and (2) a piece of 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. pedatum ; (2) a pinnule some- 

 Avhat enlarged; and (3) a piece of one more enlarged, witli tlie indusium 

 of one fruit-dot turned back to shoAv the attachment of tlie fruit. 



CIIEILANTHE8. — (1) Small plant of C. vestita; and (2) a fruit-liearing 

 pinnule, enlarged. 



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

 ^y. angustifolia ; (.3) a ])iece of the latter, enlarged ; (4) piece of the frond 

 of W. \'irginica; and (5) part of a fruiting lobe, enlarged. 



