2 THE METABOLISM OF ALGAE 



State. In books published in 1779 both Priestley^^^ and 

 Ingenhousz^^^ described experiments on the gas exchanges 

 accompanying the photosynthesis of the simple algae which 

 grew by chance in their apparatus. Priestley was sufficiently 

 interested in this 'green matter', which he doubted to have 

 'ever been properly noticed by botanists', to make further 

 experiments with it, observing, among other things, that 

 its growth was promoted by certain organic materials. 

 Priestley also determined the composition of the gas en- 

 closed in the bladders of marine algae. Ingenhousz made 

 fewer experiments with algae but realized more of their 

 possible role in the economy of nature, as is evident from 

 the sentence which is quoted at the beginning of this book. 



As in physiology generally, further progress in the study 

 of the metabolism of algae had to await the development 

 of the physical sciences and during the greater part of the 

 nineteenth century algae were studied almost exclusively 

 from morphological and taxonomic points of view. Thus 

 Sachs-^® in his text-book of plant physiology, published in 

 1882, used algae as examples wherever possible but was 

 able to say very little about their metabolism beyond 

 making the generalization that it essentially resembles that 

 of higher plants. Experimental investigation of algae in- 

 creased towards the close of the century but then followed 

 three principal lines which remained to a large extent inde- 

 pendent for a considerable period. 



Examination of the chemical constituents of algae was 

 until recently confined to the larger seaweeds and to such 

 smaller forms as very occasionally occur in a reasonably 

 pure state in sufficient quantity for analysis. Two classes 

 of substance have received most attention. Following the 

 description of alginic acid by Stanford in 1883,^^^ many 

 studies of the carbohydrates and related compounds present 

 in algae have been made. Other workers have been more 

 interested in the pigments which form such a striking 

 feature of these organisms. The work of Willstatter and 

 Stoll published in 1913^^^ is of particular importance in 

 forming the basis of our present-day knowledge of algal 

 pigments. Only recently has interest in the nitrogenous and 



