l INTRODUCTION. 



importance to be mentioned here, Ray's " Synopsis," which 

 was published in 1724, and Dillenius' " Historia Muscoruin ' 

 in 1741. Each of these, as far as they can be identified, 

 included somewhere about twenty species of Fresh-Water 

 Algaa. 



The epoch commences in reality witli 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 witli 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 Algte until the climax 

 was attained by the publication of Dillwyn's " British Con- 

 fervas ' in 1809, with 88 species enumerated. 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 Alga3 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 Alga3, 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 Algse, 

 Greville's " Flora Edinensis ' in 1824 had 50 species, the 



