86 



MARSILEACEAE 



[CH. 



a downward-directed, hypobasal, root- forming half. The relations of the 

 growing embryo will therefore be as in Fig. 468. The prothallus grows for 



468. A, embryos of Marsilea vestita. (After Campbell. 

 They are orientated in their probable natural position, since 

 the oval megaspore will normally lie fiat on its side, and the 

 prothallus is apical. B, median longitudinal section of a young 

 sporophyte and megaspore of Piliilaria. (After Campbell, 

 but orientated as it would be in nature.) ( x 70.) 



a time and protects the sporeling, while the nourishment is derived from the 

 large storage-spore till the sporeling is established. 



Comparison 



The relation of the Marsileaceae to the Schizaeaceae has been definitely 

 suggested and supported, chiefly by the observations of Campbell. The 

 essential facts are well known for the two families, and the most important 

 of them have been stated in a condensed form in the preceding pages. 

 Numerous details less direct in their bearing have been omitted, but are 

 readily accessible in the works referred to at the end of this chapter. 

 Systematic comparison of the two Families, taking up the several criteria in 



