730 EXPLANATION OF THE PLATES. 



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. XIII. 



BCHIZiEA. — Plant of S. pusilia, Pursh ; a fertile pinna with eleven sporapgia (1), magni- 

 fied ; and a separate sporangium (2), more magnified. 



LYGODIOM. — 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 Claytoniana, L. (1), with a fertile and a sterile 

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



BOTRYCHIUM. — 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 Equisetacese, L-ycopodiaceae, and 

 Hydropterides. 



Tab. XIV. 



EQUTSETUM. — Upper part of fertile plant of E. limosum, 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. 



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

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



8ELAGINELLA. — 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. 



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

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

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

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



