SALVINIACEAE 



61 



particularly exemplified in the female sporocarp of Azolla, where the number 

 has sunk to a single one : the latter in the male sorus of Salvinia, which 

 shows the unusual phenomenon of branching of the pedicels. Since the 

 annulus is absent, there is no ready clue to the orientation of the sporangia, 

 and it may be a question whether in itself the basipetal succession of origin of 

 the sporangia is a real index of affinity : it is one of those characters which 

 might readily appear in several distinct evolutionary lines. But taken with 

 the other characters of the sorus, and the fact that in these plants the 

 basipetal succession is not always strictly maintained, and does not appear to 

 be of any great practical importance, its existence in the Salviniaceae may 

 be regarded as a survival of an ancestral character. The soral characters 

 I would all harmonise with the view that the Salviniaceae are a series of 

 organisms related to the Gradatae, but subjected to modification consequent 

 upon their aquatic habit, and upon their assumption of the heterosporous 

 state. 



