EXPLANATION OF THE PLATES. 70] 



Tab. XVin. 



CYSTOPTERIS. — Piece of the frond of C. bulbifera, -BernA. (1); a lobe in fruit (2), 

 enlarged ; and a small portion more magnified (3), bearing a fruit-dot with 

 its indusium thrown back. 



WOODSIA. — Small frond of W. glabella, R. Br. (1); a part of a fruiting pinna of 

 the same (2), magnified; and a separate indusium (3), more magnified; a 

 piece of a fruitful pinnule of W. obtusa, Torr. (4), enlarged; and a fruit with 

 the opened indusium beneath (5), more magnified. 



ASPIDIUM. — Pinna of A. (Dryopteris) marginale, Swartz (1); and a magnified 

 fruiting portion (2); piece of A. (Polystiohum) acrostichoides (3); and a 

 small fruiting portion (4), magnified. 



ONOCLEA. — Sterile and fertile frond of 0. sensibilis, L. ; front view of a fruiting 

 contracted pinnule, enlarged (1); and the same laid open and viewed from 

 the other side (2): on one lobe the sporangia are removed from the veins. 



Tab. XIX. 



SCHIZJiA. — Plant of S. pusilla, Pursh., of the natural size; a fertile pinna with 

 eleven sporangia (1), magnified; and a separate sporangium (2), more mag- 

 nified. 



LYGODIUM. — Summit of frond of L. palmatnm, Swartz (1), with fertile and 



sterile divisions; a fruiting lobe enlarged (2), with two of the lower scales, or 



indusia, removed, displaying a sporangium under each; and a sporangium 



more magnified (3). 

 OSMUNDA. — Small piece of the frond of 0. Claytoniana, L. (1), with a fertile and 



a sterile pinna; a portion of the fruit magnified (2); and one sporangium more 



magnified (3).v 

 BOTRYCHIUM. — Plant of B. lunarioides, Swartz; and a portion of the fruit (1), 



with six sporangia, magnified. 

 OPHIOGLOSSXJM. — Frond of 0. vulgatum, L. ; and a portion of the fruiting spike 



enlarged (1). 



Genera of Equisetacese, Lycopodiacese, &e. 



Tab. XX. 



EQUISETUM. — Upper part of fertile plant of E. limosura, L. (1); one of the 

 shield-shaped scales or receptacles of the spike, with the six sporangia under- 

 neath (2), enlarged; same seen from below, discharging the spores (3); a 

 magnified spore with the club-shaped filaments spreading (4); and (5) the 

 same with the filaments coiled up. 



LYCOPODIUM. — Plant of L. Carolinianum, L. ; and (1) a magnified scale of the 

 spike removed, with the sporangium in its axil, discharging powdery spores. 



SELAGINELLA. — Plant of S. rupestris, Spring; part of a fertile spike, en- 

 larged (1) ; scale from the upper part of it (2), with its sporangium, oontam- 

 ing innumerable powdery spores; scale from the base (3), with its sporangium 

 containing few large spores; and (4) three large spores. 



ISOETES. — Plant of I. lacustris (1); sporocarp containing the minute spores, cut 

 across (2), enlarged; same divided lengthwise (5); sporocarp with the large 

 spores, divided lengthwise (3); and (4) three large spores more magnified. 



AZOLLA. — Plant (1); a portion magnified (2). with two kinds of organs; sterile 

 sporocarp, or antheridium, more magnified (3); fertile sporocarp more mag- 

 nified (4); the same burst open, showing the stalked sporangia (6); one of 

 the latter more magnified (6); another bursting (7); and three spores (8), 

 beset with bristles. 



