EUPHYCOPHYTA I23 



(c) Cyclosporeae : 

 Plants possessing a diploid generation only, (e.g. Fucales). 



In any consideration of phylogenetic problems there is really 

 very little difference between the two methods of classification. 



The Phaeophyceae are extremely widespread and are confined 

 almost entirely to salt water, being most luxuriant in the colder 

 waters, though the genera Heribaudiella, Pleurocladia and Bodan- 

 ella, six species of Ectocarpus and Sphacelaria fluviatilis occur in 

 fresh water. All of these except the Sphacelaria belong to the Ecto- 

 carpales and many of the records come only from China. 



Some of the species of brown algae exhibit morphological varia- 

 tions and it has been shown that these may depend on (a) season of 

 the year, and (h) nature of the locaHty. Church (1920) has given us 

 an elaborate account of the morphology of the Phaeophyceae, and 

 he suggested that if a brown flagellate came to rest it could develop 

 in one of three directions to give : 



(a) Uniseriate filaments which occupy a minimum area and 

 obtain maximum light energy per unit of area, growth being 

 either distal or intercalary. 



(fe) A mono- or polystromatic thallus which occupies a maxi- 

 mum area and obtains a minimum hght energy per unit of area. 



(c) Mass aggregation. 



A morphological examination of the brown algae will show that 

 development has taken place along each of these directions, often 

 resulting in plant bodies of a complex construction, and the follow- 

 ing types can be recognized among the various species : 



(a) Simple filaments (e.g. Acinetospora). 

 ih) Branched filaments (e.g. Pylaiella). 



\c) Erect filaments arising from a prostrate thallus (e.g. Myrio- 

 nema), 



(d) Interwoven central filaments {cable type, e.g. Myriogloia). 



(e) Prostrate portion only {reduced filamentous or cable type, 

 e.g. Pkaeostroma). 



(/) Filaments uniting to form a sphere {hollow parenchymatous 



or modified cable type, e.g. Leathesia). 

 {g) Multiseptation of primary cable type (e.g. Chorda), 

 {h) Erect filaments with cortication {corticated type, e.g. 



Sphacelaria). 



