CULTIVATING ALGAE — MEIER 375 



same struggle for existence is taking place in the drop of water 

 that occurs in our own world. 



It is impossible to determine the reactions of an alga to external 

 conditions such as nutrition, temperature, light, and humidity when 

 it is growing in a culture with dffferent algae or other organisms. 

 For although the tares were allowed to grow with the wheat until 

 the harvest, they undoubtedly harmed the crop by reducing the 

 amount of nutrient and crowding out the less robust wheat plants. 

 And when growing with other organisms, the alga chosen for study 

 may fare as the seed that fell among the thorns. If a standard solid 

 milieu or substratum is chosen on which each alga is grown sep- 

 arately, the alga can derive full benefit from the nutrient conditions, 

 but if bacteria or yeasts are allowed to grow in a culture (the me- 

 dium of nutrition for the development of an organism) with an alga, 

 it is quite probable that they will act upon the nutrients so as either 

 to stimulate or harm the growth of the alga. Fungi are the worst 

 foes of pure cultures, for if once they enter the culture the alga is 

 soon completely overgrown by them. As algae grow more slowly 

 than fungi, bacteria, or yeast, they run a greater risk of contamina- 

 tion. Algal cells are often coated with bacteria. The culture me- 

 dium must be as unfavorable as possible to the growth of both 

 bacteria and fungi, yet so constituted that it will not injure the 

 delicate algal ceils. The most rigid care must be employed in the 

 preparation of sterile culture media. 



In the time of Kiitzing and Von Niigeli, who contributed largely to 

 our early knowledge of algae, the boundaries between genus, species, 

 and variety were not very clearly defined. Many of the lower forms 

 of green algae such as Chlorella, Protococcus^ Gystococeus^ and Chla- 

 tnydomonas are so similar when found growing together in a pond 

 or a swamp that even with the aid of the highest power of the 

 microscope it is practically impossible to distinguish between them. 

 But when cells of each one of these forms are separated and grown 

 on solid media of similar concentration of nutrients, the colonies 

 that develop by a division of cells show striking dissimilarities. 

 These differences may occur in color, size, shape, and consistency of 

 the colony, which is composed of millions of similar cells of the same 

 species and variety. 



There have been three corresponding conflicts in the botany of 

 lower plants; in fimgi, in bacteria, and in algae. The same issue 

 has been at stake in each one, which resulted in the adoption and 

 development of a scientific method for the study of lower organisms— 

 the pure culture method. 



In algology, as in the fields of bacteriology and mycology, the 

 classification of algae, bacteria, and fungi was originally based on 



