be 
st INTRODUCTION. 
importance to be mentioned here, Ray’s “Synopsis,” which 
was published in 1724, and Dillenius’ “ Historia Muscorum ” 
in 1741, Each of these, as far as they can be identified, 
included somewhere about twenty species of Fresh-Water 
Alge. 
The epoch commences in reality with Hudson’s “ Flora 
Anglica,” the first edition of which is dated 1762, and contains 
about 25 species. Then came the first Edition of Withering’s 
“Arrangement of British Plants” in 1776; Lightfoot’s 
“ Flora Scotica’” in 1777, also with 25 species; Robson’s ° 
“ British Flora” in the same year, with 26 species; the 
second Edition of Hudson’s “ Flora Anglica” in 1778; 
Relhan’s “ Flora Cantabrigensis” in 1785, with 12 species; 
and Sibthorp’s “ Flora Oxoniensis ” in 1794, with 7 species. 
This brings us to the third Edition of Withering in 1796, with 
38 species; followed by Abbot’s “Flora Bedfordiensis” in 
1798, with 14 species ; and Hull’s “ British Flora” in 1799, with 
34 species. These were all the predecessors of Dillwyn, and did 
not achieve much for the Fresh-Water Alge until the climax 
was attained by the publication of Dillwyn’s “ British Con- 
ferve ” in 1809, with 88 speciesenumerated. The first Edition 
of ‘ English Botany” had already commenced in 1790, ex- 
tending to 1814, but it was not until after the appearance of 
Dillwyn’s work that the Alge of the British Botany were 
published, ultimately including about 100 species. Undoubtedly 
Dillwyn was therefore the parent of a systematic study of the 
British Fresh-Water Algw, and with him the first epoch 
culminated. 
The second epoch commenced well with the continuance of 
“‘ English Botany,” and then followed several Botanists whose 
influence has passed down even to our own times. Following 
the example of the first epoch, we may enumerate the most im- 
portant of their works. The “ Midland Flora” of Purton in 
1821 only includes about 14 species. Hooker's “ Flora 
Scotica” in 1821 about 39 species; Gray’s ‘ Arrangement ” 
in 1824, was confessedly devoted chiefly to systematic classifica- 
tion, including nominally 103 British Fresh-Water Alge. 
Greville’s “ Flora Edinensis’”’ in 1824 had 60 species, the 
