“ Histoire des Conferves d’Eau Doucc,” — admirable, when the
epoch at which it was undertaken, and the means at his disposal,
are considered. “ I wish,” he says, at p. 8., “ that those who
love Botany may see what are our riches in this respect, and
what are the discoveries reserved to their perseverance :
now tha t the way is open, more persons should engage themselves
in the study of these objects, and they should be more
rapidly studied. I f this work excites the attention of the
public, there should appear on all sides observations on new
Conferva and there will be announced, perhaps, productions
more singular than those which I describe. This taste for
research will not he confined to this one genus, but it will
extend to other neighbouring genera, which equally require
to be studied; and this beautiful part of Botany will be insensibly
draivn from the confusion in which it has for so long
a time been found.”
An additional reason why the knowledge of the freshwater
Alga, and particularly the Confervoid division of th a t tribe,
should for so long a time have remained in such a confused
and imperfect state, consisted in the want of a due appreciation
of the value of the characters founded on their reproduction,
these being of more importance, in the establishment of the
different families, genera and species, than all the other signs
and characters derived from attention to other conditions and
appearances of these plants. To a right appreciation of the
importance of attention to the reproduction of the Conferva
it is that the superiority of Vaucher’s «Histoire des Conferves
d’Eau Douce, ” is mainly owing, over other works on the same
subject, that close and amiable observer having made— and he
was the first, and almost the only one to do so — a knowledge
of their reproduction his chief aim and study. Thus the
majority of the earlier observers, and some even of recent
date, have deemed it sufficient to describe any plant of this
class merely from the appearance which it presented on a
first examination, without any reference to the stage of de-
velopement or condition of th a t p la n t; and have of course
expected tha t the productions thus imperfectly recorded
should have been recognized with facility by subsequent invcstigators,
and handed down to posterity. Such expectations,
however, it is impossible to realise; and I agree with
Vaucher in thinking, that the wisest course to adopt would be
(except in some few cases, where the jiroductions can with certainty
he determined by other characters,) to notice only those
species whose reproduction has been satisfactorily made out.
In the present work, the necessity for which is in a
measure indicated by the preceding remarks, the characters
developed in the state of reproduction are relied upon, in the
framing not merely of the families and genera, but also in the
definition of species, for which they are even more valuable.
In this Introduction it is not intended that a fu l l description
should be given of the different modes of reproduction
and of the structure of the freshwater Alga, the details of
these coming under consideration with more propriety when
the divisions into families, genera, and species are treated of.
The general particulars of each will, hoivever, be now noticed.
Linna5us supposed tha t all vegetable productions owed
their perpetuity to sexes: he did not, however, assign in his
system any fructification to the Conferva. Had Linnajus,
nevertheless, been aware of the highly curious and interesting
facts which more recent investigation has made known, viz.,
of the phenomenon of the union of tAvo cells, either in different
or in the same filaments, which so frequently occurs
amongst the Conferva (see Plates 30 —50. and33.), he Avould
doubtless have regarded this commingling as not merely
strengthening, but proving the correctness of his views of the
sexual character of all plants. But it is to be questioned
how far the fact ju st alluded to would bear any such interpretation,
its tendency in support of the opinions of the illustrious
Swede being completely neutralised by our acquaintance
Avith other facts, and chiefly with this, viz., tha t in a considerable
proportion of freshwater species, and probably in the
entire of the marine Conferva, no such conjunction of filaments
or commingling of the contents of two cells occurs, all the requisites
for the continuance of these being indisputably contained
within each cell, no exterior organs of reproduction ever
having been discovered in the vast majority of these. The
B 2