Would not dream of arguing with an expert, it was obviously the word required....Chambers, wrong?? every possibility.
i;o THE SALVINIACE>E.
have arisen through some such ancestor as the floating
fern, though as a matter of present relationships the
species of this group appear to have closer affinities for
the filmy ferns (Hymenophyllacese), especially as regards
the formation of their sporocarps. In any event they are
probably more closely allied to the ferns than any of the
other fern allies except the Marsiliaceae, and some are
so much like ferns in their structure as to have received
the common name of water-fern. As a class they are,
with the Marsiliaceae, sometimes spoken of as the
Hydropterids (which may be translated as water-ferns),
or as Rhizocarps, which refers to the way the sporocarps
are borne in these families.
Taken from:
http://www.ebooksread.com/authors-eng/willard-nelson-clute/the-fern-allies-of-north-america-north-of-mexico-hci/page-10-the-fern-allies-of-north-america-north-of-mexico-hci.shtml