376 ANNUAL EEPORT SMITHSONIAN INSTITUTION, 19 3 2 



knowledge gained by direct observation. The need of isolation of 

 a single individual for the study of its life history and independent 

 reaction to such external conditions as light, temperature, humidity, 

 and nutrition was very slowly realized by the algologists. Just as 

 in bacteriology and mycology, polymorphism, the idea that lower 

 forms of algae change into higher forms of algae during their 

 development, caused confusion in efforts toward classification. For 

 instance, the round cells of Protococcus were claimed to change into 

 the long, slender, needlelike cells of Raphidium at some stage of their 

 existence. Pleurococous^ a unicellular form, was even accused of 

 disguising itself for some reason as Siigeoclonium., a multicellular 

 branching filamentous form. In 1896 Klebs pointed out the fallacy 

 of these classifications by indicating that if Pleurococcus vulgaris 

 could change into a Stigeoclonium, it should be classified with the 

 branched filamentous algae, but if as claimed, Pleurococcus were a 

 degenerate form of a Stigeoclordum., the latter should be considered 

 an independent unicellular alga. Klebs emphasized the necessity 

 of direct observation of the alga growing in pure culture if the 

 exact determination of its life cycle were to be ascertained. 



Famintzin in 1871 was the first person to grow algae in water 

 cultures. The work of Knop and Stohmann with phanerograms 

 in inorganic salt solution as vvell as the experiments carried on by 

 Pasteur and Rolin on lower fungi inspired him to place cells of 

 an alga that he had selected for study in hanging drops of solutions 

 of inorganic salts on a microscope slide. A solution that has proved 

 admirably fitted in nutritive value to the growth of the algae is 

 a modified Knop solution made up in the following proportions and 

 then diluted to one-third : 



Calcium nitrate 1. 00 gram 



Potassium chloritle 0.25 do 



Magnesium sulphate 0. 25 do 



Potassium acid phosphate 0. 25 do 



Distilled water 1 liter 



Ferric chloride a trace 



If the algae are grown in cotton-stoppered glass flasks holding 100 

 or 200 cubic centimeters of this liquid solution, and at the same time 

 on solid medium made by adding 2 per cent agar plus 2 per cent 

 glucose to the mineral solution, an excellent idea can be formed of 

 the behavior of the individual algae in solution as well as of the dis- 

 tinctive characteristics of each colony of algae on solid medium. As 

 the immigrant placed for the first time in his new environment has 

 the greatest difficulty in adjusting himself to the change in diet, so 

 the alga reacts to a similar change. On solid media the colonies form 

 disks that vary from green to bright orange in color, that are gelat- 



