EXPLANATION OF PLATE XXL 



EQUISETUM.— (1) Upper part of fertile plant of E. limosum; (2) one of 

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

 underneath, enlarged; (3) same seen from below, discharging the spores; 



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



(5) the same with the filaments coiled up. 



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

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

 spores. 



SELAGINELLA. — Plant of S. rupestris ; ( 1 ) part of a fertile spike, enlarged ; 

 (2) scale from the upper part of it, with its sporangium, containing innu- 

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

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



ISOETES. — (1) Plant of I. lacustris; (2) sporocarp containing the minute 

 sjjores, cut across, enlarged; (5) same divided lengthwise; (3) sporocarp 

 with the large spores, divided lengthwise; and (4) three large spores 

 more magnified. 



AZOLLA. — (1) Plant; (2) a portion magnified, with conceptacles of both 

 kinds; (3) the macrosporic one, more magnified; (4) the microsporia 

 one, more magnified ; (5) the same burst open, showing the stalked micro- 

 sporangia; (6) one of the latter more magnified; (7) another bursting; 

 and (8) three masses of microspores beset with glochidiate or barbed 

 bristles. 



