730 EXPLANATION OF THE PLATES. 



ONOCLEA. Sterile and fertile frond of 0. sensibills, 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. XIII. 



BCHIZJEA. Plant of S. pusilla, Pitrth ; a fertile pinna with eleven sporangia ;1), magni- 

 fied ; and a separate spoi-angiura (2), more magnified. 



LYOODIUM. Summit of frond of L. palmatum, Swartz (1), with fertile and sterile divis- 

 ions ; 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 Clay toniana, L, (1), with a fertile and a sterile 

 pinna ; a portion of the fruit magnified (2) ; and one sporangium more magnified (3). 



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

 six sporangia, magnified. 



OPHIOGLOSSUM. Frond of 0. vulgatum, L. ; and a portion of the fruiting spike en- 

 larged (1). 



Genera of Equisetaceae, Lycopodiaceae, and 

 Hydropterides. 



TAB. XIV. 



EQUISETUM. Upper part of fertile plant of E. liinosum, L. (1) ; one of the shield-shaped 

 scales or receptacles of the spike, with the six sporangia underneath (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. 



i,YCOPODIUM Plant of L. Carolinianum, L. ; and (1) a magnified scale of the spike 

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



8ELAG1 NELL A. Plant of S. rupestris, Spring; part of a fertile spike, enlarged (1) ; scale 

 from the upper part of it (2), with its sporangium, containing 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 minute spores, cut across (2), 

 enlarged ; same divided lengthwise (5) ; sporocarp with coarse spores, divided length- 

 wise (3) ; and (4) three coarse spores more magnified. 



A.ZOLLA. Plant (1) ; a portion magnified (2), with two kinds of organs ; sterile sporocarp 

 or antheridium, more magnified (3) ; fertile sporocarp more magnified (4) ; the sauie 

 burst open, showing the stalked sporangia (5) ; one of the latter more magnified (6) ; 

 another bursting (7) ; and three spores (8), beset with bristles. 



