EXPLANATION OF THE PLATES. 



ISO ETES. Plant of I. lacustris (1) ; sporocarp containing minute spores, cut across (2\ 

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

 lengthwise (8) ; and (4) three coarse spores more magnified. 



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

 or antherfdium, more magnified (8) ; 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. 



