SALVINIACEAE 611 
particularly exemplified in the female sporocarp of Azod/a, where the number 
has sunk to a single one: the latter in the male sorus of Sa/vinia, 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 
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. 
