PREFACE. 



T'HE object of the present volume is to give the student a 

 concise account of the structure, habits and life-histories of 

 Freshwater Alga?, and also to enable him to place within the 

 prescribed limits of a genus any Alga he may find in the fresh 

 waters of the British Islands. 



Although it may seem incongruous to treat of freshwater Algse 

 apart from marine ones, there are many excuses for the production 

 of a special treatise on the freshwater, forms. Few genera of 

 Algae, and still fewer species, exist both in salt and fresh water, 

 and the vast majority of marine Alga^ are very different in nature 

 from those inhabiting fresh water. 



The need for a book of this kind is very great, owing to the 

 rapid strides made in the investigation of this class of plants 

 during the last twenty years. To identify even many of the 

 commonest of freshwater Alga? one has at present to be fully 

 conversant with most of the recent phycological literature, and 

 I have endeavoured in this volume to give a general account of 

 those facts concerning the British species which will be of most 

 assistance to a diligent student. 



Many facts and suggestions concerning the life-histories, de- 

 velopment, and relationships of freshwater Algae are here brought 

 forward for the first time, and with few exceptions the figures are 

 original, pains having been taken to state as far as possible the 

 localities from which the specimens were collected. The figures 

 are careful and accurate drawings to scale, and they are in no wny 

 diagrammatic. A few stages in the life-histories of various Alg;c. 

 and certain figures showing structural peculiarities, have been 

 copied from the original drawings of other authors, but in each 

 case this has been specially mentioned. 



