Phylogeny 21 



types, but the fact must not be overlooked that these lowly types, 

 although they may have undergone many modifications, still 

 persist, and great care should be taken not to confound them with 

 those stages in the life-histories of the higher types which present 

 so many resemblances to them. 



THE PHYLOGENY AND CLASSIFICATION OF THE 

 FRESHWATER ALG.E. 



The researches and discoveries of the last few years have 

 certainly thrown much light on the affinities of many genera and 

 families of Algae, and constitute a very great advance in our 

 knowledge of the phylogenetic relationships of these plants. It is 

 by no means an easy task to give even a mere outline of the 

 suggestions which have at different times been put forward as to 

 the evolution of freshwater Algae, but one derives great assistance 

 from two recently published papers, one by Chodat 1 and the other 

 by Blackman 2 , containing not only a summary of much of the work 

 bearing on this difficult problem of phylogeny, but putting forward 

 some well-founded suggestions as to the same. 



In the succeeding brief account of the evolution of freshwater 

 Algae I have followed very largely the suggestions of Borzi, 

 Blackman, Bohlin and others, with certain alterations based upon 

 my own experience 3 . 



Taking first the Chlorophycese or green Algae, which a few 

 years ago were in a chaotic condition, we find that this chaos has 

 been greatly reduced to order and that the affinities of many of 

 these plants have been clearly demonstrated. The four groups 

 of the Confervoideae, Conjugates, Siphoneae and Protococcoidese, into 

 which the green Algae have been usually classified, must be con- 

 siderably modified in view of recent researches. The Conjugates 

 and the Siphoneae will remain as distinct and natural orders of the 

 green Algae, the former chiefly by reason of their reproduction and 

 the latter on account of their coenocytic structure, but the Con- 

 fervoideae and Protococcoideae were unquestionably unnatural 



1 Chodat, 'On the Polymorphism of Green Algaa and the Principles of their 

 Evolution,' Ann. Bot. xi, 1897. 



2 F. F. Blackman, 'The Primitive Algne and the Flagellata. An Account of 

 Modern Work bearing on the Evolution of the Algse,' Ann. Bot. xiv, 1900. 



3 In 'Lectures on the Evolution of Plants' by D. H. Campbell (Macmillan 

 Company, New York, 1889), there is a chapter on Algae (pp. 48 79) with a scheme 

 of evolution (p. 79), but the latter appears to be largely based upon erroneous 

 conceptions of the relationships of these plants. 



