Fig. 4: a and b, Psilotum nudum: a, habit, x ^,4; b, sporangium, x 4. c, Marsilea 

 Fournieri: c, habit, x %, with leaf, x 2. d, Marsilea mexicana: d, habit, x %, with leaf, 

 X 2, and sporocarps, about x 2V.. e, Ophioglossum Engelmannii: e, habit, x %, with 

 section of sterile leaf blade enlarged. 



