774 THE AMKRICAX XA ri RALlsr. [Vn,,. XXXVIII. 



in some species (tf Schizua. where tlie leaf is dichotomously 

 divided, but the fertile sei^ments are pinnate. 



A comparison of the vegetative organs of the Marsiliaceae 

 and Schizaeaceae shows equally marked resemblances. The 

 creeping rhizome of Marsilia and Pilularia is remarkably similar 

 to that of Schizaea and certain species of Aneimia (Fig. 7), as 

 may be clearly seen from the figure. The leaves also show 

 interestmg resemblances. Thus the filiform leaf of Pilularia 

 finds Its exact counterpart in the sterile leaves of Schiztea pnsilla, 

 while the four-lobed leaf of Marsilia is comparable to such spe- 

 cies as Scliizcea pcnnu/a, with dichotomously branched lamina. 

 The venation in SchiZcca and Aneimia is characteristically dichot- 

 omous, close!) lesembhng that of Marsilia. Except in Lygo- 

 dium, the pinnate venation 

 found in the majority of the 

 ferns does not occur among 

 the Schizaeacese. 



So far as I am aware, no 

 direct comparison of the spo- 

 rangia in the two families has 

 been made, although the early 

 stages of the sporangium have 

 been carefully studied. The 

 Schizaeaceae differ from all 

 the other ferns in the very 

 peculiar form of the sporan- 

 gium which is strongly oblique 

 and has a terminal annulus. 

 The sporangia of Pilularia 

 americana and Marsilia ves- 

 tita were examined, and it 

 was found, especially in the 

 case of the former, that the 

 sporangia resembled strongly 

 wi^.c ui LUC c>cnizaeacea2. In Marsilia the closely packed micro- 

 spore rendered it difficult to make out the form of the parietal 

 cells, but in Pilularia the spores are widely separated and the 

 form of the parietal cells is easily seen when the sporangia, 



