474 HYDROPTERIDEAE [CH. 



Schizaeaceae than to any other family of homosporous ferns ^- 

 Their heterospory, the production of sporangia in closed fruit- 

 like sporocarps, and the anatomical features associated with 

 existence in marshy habitats, tend to obscure the resemblances 

 to the true ferns. 



The genus Marsilidium proposed by Schenk^ for a piece of 

 an axis, bearing apparently a whorl of six leaflets, from the 

 Wealden of Osterwald, cannot be regarded as satisfactory 

 evidence of the existence of the Marsiliaceae in the Wealden 

 flora of North Germany. 



The six leaflets of Marsilidium specioswn, having a length 

 of 5 cm., are similar in shape to the four leaflets of recent 

 species of Marsilia, but they differ in the repeated dichotomy 

 of the veins from the reticulate venation of the recent forms. 

 It is worthy of note, however, that in Lindman's Brazilian type 

 Regnellidium diphyllum (fig. 326, A), the leaflets are characterised 

 by dichotomous and not by anastomosing veins. 



Hollick" has described some impressions of imperfect orbicular 

 leaves with a "finely flabellate obscurely reticulated (?) venation" 

 from Cretaceous rocks of Long Island as Marsilia Andersoni, 

 but these are too fragmentary to be accorded this generic 

 designation. My friend Dr Krasser informs me that he is 

 describing some well-preserved leaves from Cretaceous beds of 

 Grtinbach in Lower Austria as Marsilia Naihorsti*. He com- 

 pares these with the recent form Marsilia elata, a variety of 

 M. Drummondi. 



Another Lower Cretaceous species Marsilia perucensis has 

 been figured by Fric and Bayer' as a stalked fruit-like body 

 from Bohemia. This was originally described by VelenovskjF as 

 M. cretacea, but under this name Heer" had previously recorded 

 a supposed sporocarp from Greenland. These fossils have little 

 claim to recognition as examples of Marsiliaceous plants. 



The fragment figured by Heer'' from Tertiary rocks of 



1 Campbell (04) ; Bower (08) p. 551. 2 Schenk (71) p. 225. 



' Hollick (94) PI. Lxxi. ■» Mentioned by Krasser (06) in a preliminary note. 



6 FriiS and Bayer (01) p. 86, flg. 34. e Hear (82) PL xvi. 



' Heer (55) A. Vol. m. p. 156, PI. cxlt. fig. 35. 



