BEITISH FEESH-WATEE ALGiE.
INT EODU C TION .
“ Fre sli-Wa te r Alg» " is confessedly an artificial arrangement
which demands apology, but can scarcely receive
justification. The only excuse which can be offered is, th a t it
serves the purpose of those for whom the present work was
written, namely, the Microscopists who desire some acquaintance
with the organisms met with in their excursions to ponds
and ditches. Fo r the absolutely scientific algologist it will
only be fragmentary, although it is by no means a solitary instance
in which the Fresh-Water Algee have been made the
sole subject of a book, to the exclusion of marine species.
Indeed, the restriction of Harvey’s “ Phycologia Britannica ”
to marine algte, with but very few exceptions, left at least an
excuse for attempting to supply the deficiency.
The historical portion of this introduction may be speedily
summarized by dividing it into three epochs of about forty years
each, the first being limited by the publication of Dillwyn’s
“ Conferv«,” the second by Hassall's “ Fresh-Water Algse,”
and the third by the present work.
Prio r to the first epoch there were but two works of sufficient