INTRODUCTION. 37 



but furnishes one or more species, and even our mineral 

 springs are not entirely free from them. From the uniform 

 nature of the element which the majority of the freshwater 

 Alga inhabit, it may be confidently anticipated that very 

 many of the species described in this work will, when the 

 Alga come to be studied with that diligence and care which 

 they so well merit, be found in most of the continental 

 countries. Of the species described by Yaucher, a consider- 

 able proportion are likewise indigenous to Great Britain. 



Most of the freshwater Conferva, when in a healthy state, 

 are of a green colour, the shade being often extremely rich 

 and beautiful, but varying with the condition of the species, 

 and with the species themselves. The occurrence of this 

 colour is comparatively rare amongst the marine Alga, in 

 which it is usually more or less red or brown, the colouring 

 matter being operated upon probably by free acids in the salt 

 water. 



Sometimes the Conferva are diffused through the waters 

 of a pond or lake, imparting to it a bright green colour, and 

 causing it to resemble so much of the purer element the 

 sea. At others, the filaments of a number of different species 

 will become entangled, and float together upon the surface of 

 the water, wafted hither and thither by the wind, like a 

 beautiful cloud, the softness and richness of the tints of which 

 a painter would be immortalized could he imitate. It is only 

 during the early spring months, however, that the Conferva 

 retain this depth and beauty of colouring; for under the 

 influence of the rays of the summer sun, they very soon fade 

 and bleach, becoming ultimately, when the water in which 

 they dwell has evaporated, converted into the paper-like 

 substance which has recently attracted so much attention on 

 the Continent; indeed, so like to artificial paper is this 

 natural formation, that I feel assured an useful paper might, 

 by an artificial process, be made during the summer months 

 out of many abundant species of Conferva. 



The Conferva, like most other productions, whether animal 

 or vegetable, whose organization is feeble, cling tenaciously 

 to life ; thus, they may be torn and cut up into a thousand 



D 3 



