THE PHYLOGENY AND INTER- 

 RELATIONSHIPS OF THE GREEN ALG^E 



By F. E. FRITSCH, D.Sc, Ph.D., F.L.S. 



University of London, University and East London Colleges. 



In any attempt to trace the evolution of the vegetable kingdom 

 a considerable amount of interest must naturally centre about 

 its simplest representatives, which may justly be regarded 

 as having some resemblance to the primitive ancestral forms 

 from which the higher types have sprung. The lowest forms 

 of plants are at the present day placed in the class of the 

 Thallophyta, which embraces the two large divisions of the 

 Algae and Fungi. These are separated largely on physiological 

 grounds, the latter being devoid of the chlorophyll, possessed 

 by the Algae and the remaining classes of the vegetable 

 kingdom. The absence of chlorophyll in the Fungi and the 

 consequent inability to manufacture their own food-substances 

 in the way characteristic of the majority of plants have led to 

 far-reaching peculiarities. As our knowledge of the Fungi 

 improves and a better insight into these peculiarities is obtained, 

 it is, however, becoming increasingly clear that we shall soon 

 have to abolish the artificial distinction between Algae and 

 Fungi, and recognise the fact that the latter are merely parasitic 

 or saprophytic degenerates of diverse lines of algal evolution 

 (cf. especially Davis 19, 1 Lagerheim 45, Lotsy 46, Stevens 65). 

 In any case, however, the Fungi must be regarded as a side- 

 line, and it is unnecessary to consider them in connection with 

 any theory as to the mode of evolution of the higher green 

 plant, which no doubt arose directly from algal ancestors. 



The Algae were formerly classified in four groups according 

 to the colour of the pigment in their chloroplasts : the green 

 Algae or Chlorophyceae, the brown Algae or Phaeophyceae, 

 the red Algae or Rhodophyceae, and the blue-green Algae or 

 Cyanophyceae. Of these the green and blue-green forms are 



1 References to all the memoirs quoted will be found in the bibliography 

 at end of the second part of this article. 



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