Phylogeny 33 



Flagellata. Be it remembered, however, that there is no direct 

 evidence in support of the view that the CEdogoniales and 

 Conjugates are phylogenetically independent of the rest of the 

 Chlorophycese. Indeed, with regard to the Conjugates all the 

 known facts concerning them tend to show that they, at least, 

 have not had a direct origin from Flagellate ancestors. I have for 

 many years made a special study of the Conjugate, including a 

 particularly detailed investigation of the Desmidiacese, the family 

 around which all the interest of this idea is centred; and I can 

 say most emphatically that all the facts concerning these plants 

 with which I am acquainted, far from supporting the idea of a 

 Flagellate ancestry, tend to prove conclusively that this beautiful 

 family of Conjugates has originated from filamentous ancestors. 



The separation of the Conjugate from the rest of the 

 Chlorophycea? is therefore to my mind based upon an erroneous 

 supposition, and there is likewise no evidence to show that the 

 complete separation of the CEdogoniales from the rest of the green 

 Alga3 is a just one. The Heterokontae is obviously a very natural 

 class, but I have not transferred the Vaucheriacese to the Hetero- 

 kontae nor the Cladophoracese to the Siphonese. The genus 

 Prasiola has no relationship to the Ulotrichacese and I have 

 placed it in the order Schizogoniales. My arrangement of the 

 Conjugate is also quite different from that given by Blackman 

 and Tansley, particularly in the family Desmidiacese, of which I 

 have given a natural classification. 



In those facts lie the main differences between the classification 

 put forward by Blackman and Tansley and the one used for the 

 green Algae in the present volume, which is based upon a very 

 extensive and careful study of these plants for many years. There 

 will also be found many differences in the genera themselves and 

 in their disposition, as I have arranged them in a manner which I 

 consider to be much more in accordance with their affinities. For 

 example, the genera Radiofilum Schmidle and Hormospora Breb. 

 are undoubtedly feebly developed forms of the Ulotrichacese and 

 have no place in the Protococcaceae; and the same is true of the 

 genera Glceotila Kiitz. and Stichococcus Nag. Dactylothece Lagerh. 

 is an elongated Glceocystis-\ike genus and has no relationship with 

 either Dimorphococcus A. Br. or Scenedesmus Meyen ; and many 

 other instances could be quoted. 



w. A. 3 



