PREFACE 



FT is now twelve years since the publication of the author's 'Treatise on 



British Freshwater Algae' and several years since that work was sold 

 out. Since the time of its publication great strides have been made in our 

 knowledge of many groups of Algse and it is now proposed to replace the 

 'Treatise' by two works of which this is one. The present volume, contributed 

 to the series of Cambridge Botanical Handbooks, is a biological account of all 

 the Algse included in the Myxophycese, Peridiniese, Bacillariea3 and Chloro- 

 phycese, both freshwater and marine, and therefore from the biological aspect 

 more than covers the Algae dealt with in the 'Treatise.' The author has 

 also in preparation a distinct work which will be a complete systematic 

 account, with illustrations, of all the Freshwater Alga3 (with the exception 

 of Desmids and Diatoms) which are known to occur in the British Islands. 

 This is a task of some magnitude and will still take some time to complete. 



An endeavour has been made to be impersonal throughout this volume, 

 but the whole work must of necessity be largely the embodiment of the 

 views of the author. 



A chapter has been devoted to the Peridiniese because these organisms 

 are important as ' producers ' of organic substance, especially in the marine 

 plankton, and they store starch and oil as food-reserves; moreover, no 

 comprehensive modern account of the group has previously been published 

 in an English text-book. It might be suggested that the Flagellata should 

 have been included in this volume, since the majority of them are also 

 ' producers,' but the immense additions in recent years to our knowledge of 

 these organisms certainly necessitates a separate volume to do them justice. 



The greater part of this work deals with the Green Alga3. It is to this 

 group that the author has devoted most of his investigations and a number 

 of new details of classification are suggested. The treatment of this group 

 is different from that of the Myxophycese, Peridiniese and Bacillariese, being 

 sectional in character. Generalizations are well nigh impossible in such 

 a large group containing so many diverse types, and to set forth an intelligible 



