178 



MARSILEACEAE 



[CH. 



tvvo-lobed leaves (as they are permanently in Regnellidiiivi (Fig. 460)), and 

 finally four-lobed leaves; the last are those normally seen in Marsilea (Fig. 

 461): but occasionally, as in M. quadrifolia, six segments have been formed. 

 Moreover, the relation of the lobes at the base to the strand that traverses 

 the stipe is the same as that seen in the juvenile leaves of Osmunda, Botry- 

 chiuin, or Anemia (compare Vol. I, Figs, "jj, 80, 81), or even of the adult in 



Fig. 460. Regnellidium diphyUum Lind. (Natural size.) Specimen from S. Brazil. 

 From an elongated stem, with dead swimming leaves, of which only the stalks 

 remain ; aerial shoots have developed, with land-leaves, which bear the sporocarps. 

 (After Lindman.) 



A. elegans (compare Chapter XXII, Fig. 446). From these facts it follows 

 that the blade of Marsilea is dichopodially produced, as it is in so many 

 early Ferns, the branchings being one, two, three or more. But the venation 

 shows one feature of advance on the Ferns above quoted, in the marginal 

 loops by which the separate veins are linked into a closed system (Fig. 461). 

 The adult leaves of the family probably illustrate a degradation series from 



