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ON POTAMOGETON FLUITANS. 203
Moore. — 5.
WUsan.
planifolia Hook. Brandon only, Dr. Taylor and W.
DijAophijllnm ohtusifolinm Dum. Found more than sixty years
ago by Dr. Taylor near Dunkerron.
Juni/cDiKtmiia Dicksoni Hook. Connor Hill, Dr. Moore. — J,
Bantrieusis Hook. Brandon, J>r. Moore. — J. Hornschiickittna Nees.
Near Upper Lake and Tore Mtn., Killarney, 18G9, Dr. Moore.
Acroholbus nV/wHt Nees. W. Wilson, 1829; Dr. Taylor, 1841.
Scalid Hookeri Gray. One solitary female plant on Connor
Hill, 1873, Dr. Linilberg.
Aiithoceros IcBvis L. Abundant near Yentry, Dr. Liiulbcrg and
Dr. Moore, 1873.
ON POTAMOGETON FLUITANS Roth.
By William H. Beeby.
The object of the present paper is to try to throw a little
light on the proper application of this name. A good deal that
has been written on the subject hitherto seems scarcely more
than conjecture ; while a definite statement, like that of Keichenbach,
which surely deserves to be accepted or refuted, or at least
to be remarked upon, is passed over in silence.
The freely-fruiting plant of the Continent, called by many
" P.jluitans," has been assumed to be the plant of Roth ; and this
assumption once having been made, fruit is sometimes asked for to
prove that any given example is the plant of Roth ! Unfortunately
Roth did not describe the fruit at all ; and as it appears to have
been impossible to find a type specimen of Roth's plant, the conception
of the fruit of P. jliiitans Roth, can scarcely come from an
authentic source. As Roth does not give descriptions of the fruit
in this genus, the identification of his plant must, in the absence
of authentic specimens, rest on other characters and considerations.
Reichenbach (Ic. Fl. Germ, et Helv., t. 49, 48) figures two
plants which he regards as varieties of the same species, viz., his
typical sterile P.fluitans Roth, in a plate which well represents the
British plant ; and his fertile " /?. sUtyndtilis Koch." Speaking of
our sterile plant he says, " No one seems to have seen the typical
form in fruit, which is known to me in no collection." Now, where
there exist two forms, the one fertile and the other sterile, and supposed
to belong to the same species, the almost universal custom is
to call the fertile plant the type ; and it is not likely that Reichenbach
chose the opposite arrangement merely from caprice. The
inference is rather that he took the more unusual course because,
for some reason known to himself, he felt that he had no choice ;
especially when his remarks on tlie sterility of the typical form are
taken into consideration. And it may be pointed out that the idea
of sterility did not altogether originate with Reichenbach, for
Chamisso and Schlechteiidal say, " Scuiina, ex Nolte, acutiua
carinata quam uatantis, ultamcn non satis matiira observabantur."