MONOSTROMA/ 



^y 



MANY LULVACEAE 



^ .SIPHONOCLA- 

 ACEAE 



HALICYSTIS 



SIPHCNALES 



Fig. 1 86 Types of life cycle in the Chlorophyceae and their pos- 

 sible inter-relationships. RD = position of reduction division in the 



Hfe cycle. 



Rhodophyceae it is extremely difficult to accept in the case of the 

 Chlorophyceae because there are so very few examples among the 

 primitive orders, e.g. Volvocales, Chlorococcales. 



At the present time hypotheses have to be based primarily upon 

 a study of living forms. Many ancestral forms must have disap- 

 peared, and whilst there are arguments in support of the several 

 different hypotheses that have been put forward, it is believed that 

 the greatest support will be found for scheme A, with scheme D 

 representing certain parts in more detail. 



In his studies on the Rhodophyceae, Svedelius coined a number 

 of words which have subsequently come into common usage for 

 the algae: 



X 313 



