GROWTH AND METABOLISM I23 



In Chlorella vulgaris^ at least within certain limits and 

 under the particular experimental conditions used, the pro- 

 portion which fatty acids form of the total reserve material 

 changes little as the nitrogen content of the cell varies. In 

 Monodus, Trihonema and C. pyrenoidosa, however, a decrease 

 in nitrogen content produces a considerable alteration in 

 favour of lipide synthesis, whereas in Anahaena cylindrica 

 and Oscillatoria sp. there is a less marked trend in the 

 opposite direction. From this it appears that algae which 

 characteristically store lipide are able to develop the 

 mechanism for converting the primary products of photo- 

 synthesis into lipide on nitrogen starvation whereas in other 

 algae the balance of the lipide and carbohydrate synthe- 

 sizing systems is not altered to any great extent by nitrogen 

 deficiency. 



GROWTH AND METABOLISM IN THE HIGHER ALGAE 



The changes in metabolism which occur during the 

 growth of a structurally complex plant are in a general way 

 similar to those which have just been described as occurring 

 in cultures of simple algae. ^^^ However, in most multi- 

 cellular organisms the situation is complicated by the 

 specialization of tissues for particular functions. Thus, while 

 a growing point of one of the higher algae may show the 

 same type of metabolism as a unicellular alga in the expo- 

 nential phase of growth, the metabolism of other tissues 

 will be more equivalent to that of a population of single 

 cells in the stationary phase. The activities of the two types 

 of tissue cannot be considered entirely separately since 

 in the intact plant the one will be interrelated with the 

 other. 



Studies of the growth and metabolism ofthe larger algae, 

 most of which are seaweeds belonging to the classes 

 Chlorophyceae, Phaeophyceae or Rhodophyceae, have been 

 restricted because of the difficulty of growing these plants 

 under controlled conditions. Detailed accounts of growth 

 appear to exist only for certain Laminariaceae and 

 Fucaceae. (e.g. ^^2, 220^^ Since a fair amount of information 

 on both growth and chemical constitution is available for 



