WHAT ARE ALGAE 



LTHOUGH most freshwater algae are microscopic, many 

 kinds are greqarious and occur in such numbers as to 

 form the well-known and conspicuous "pond scums," 

 "water blooms," or "water mosses." A few genera are 

 individually large enough to be seen easily without the 



aid of a microscope, e.g., the stone-worts (Characeae), or some of the 



freshwater red algae such as Batiachospermum. 



If it were possible for freshwater algae to grow as large as some 

 other plants (mosses and ferns for example) and to live upon land, 

 they would be considered highly attractive indeed and would be much 

 cultivated as ornamentals. The symmetry of form and the patterns of 

 ixtemal decorations which many of them possess are not excelled by 

 the larger plants in beauty. The varied shapes of both marine and 

 freshwater algae, coupled with their many colors and hues have made 



them the subject of observa- 

 tion and wonderment for a 

 long time, especially since 

 the invention of the micro- 

 scope. Indeed, the microsco- 

 pic size of most of the fresh- 

 water algae make them all 

 the more intriguing, and 

 since the early days of the 

 first microscopical club they 

 have been used for pleasur- 

 able observation and specu- 

 lation. It is not the aesthetic 

 quality alone of freshwater 

 algae, of course, which explains the amount of interest shown them. 

 For small though they are. freshwater algae (like some of their micro- 

 scopic kin in the oceans) have their own economic importance. Their 

 relationship to aquatic biology problems of various kinds, their trouble- 

 some contamination of water supplies, and their use in general physi- 

 ological research constitute just a few of the manv aspects which 

 lead to a study of them. Purely scientific problems such as their role 

 in organic evolution, the biology of their reproduction and life his- 

 tories, and their ecology are common subjects of investigation. Al- 

 though much is still to be learned from them, the solution, or at least 

 clarification, of many problems in general biology and physiology 

 have been obtained from studies of algae. At this time, for example, 

 much attention is being given to algae in culture for the study of 

 highly important and practical problems in photosynthesis and the 

 products of algal metabolism. Some genera of unicellular algae are 



1 



