CULTIVATING ALGAE MEIER 377 



inous, button-shaped, or irregular in numerous other ways. A de- 

 signer could easily find original ideas for buttons or prints from these 

 colonial formations of millions of cells of the same species. (See 



pl.l.) 



In the solid medium described above, mineral salts and sugar are 

 not in equilibrium, consequently striking differences in the reactions 

 of the different species of algae show up very clearly. The cells 

 in the colonies differ somewhat from each other owing to the fact 

 that the colonies are composed of all ages of cells; old ones that per- 

 haps developed directly from the original inoculum beside new cells 

 that resulted from division to-day or yesterday. The cells varying 

 in age produce different excretions which modify their growth and 

 development. The disks of cells, as a rule growing centrifugally, 

 attain a size that varies with the different species, owing to the accu- 

 mulation of excretions and the growing concentration of the medium 

 caused by loss of water. Some species grow deep down into the agar 

 medium, while in others the cells are piled upon each other to form 

 little peaks, possibly because they are seeking better aeration. 



Another method found to be valuable for comparative studies of 

 algae makes use of porous clay cups. (See pi. 2.) As Livingston 

 (1908) describes, the porous cup after being sterilized in the auto- 

 clave or steam pressure cooker is filled with the nutrient solution 

 desired, stoppered with a perforated rubber stopper and connected 

 by a tube through the latter with a flask of the solution placed at 

 a lower level. It was found necessary to place the flask of solution 

 connected with the porous cup of solution in the autoclave for a 

 second sterilization. At the same time a glass jacket, larger by 2 

 centimeters in diameter than the porous cup, was sterilized in the 

 autoclave. Immediately on opening the autoclave, the glass jacket 

 was placed over the porous cup and stoppered with sterile cotton 

 at the base of the rubber cork. The whole apparatus was then sup- 

 ported by a ringstand and allowed to cool. The jacket was removed 

 long enough to allow the quick inoculation on the cup of several dif- 

 ferent algae. The differences in growth, color, and consistency of 

 the algae for the nutrient solution used were plainly visible through 

 the glass shell. Because of the careful sterilization and by keeping 

 the cup closed inside the glass jacket, it was possible for the algae 

 to grow vividly on the cup for a month's time without signs of 

 contamination. 



The first successful attempt at isolating and growing algae in 

 pure culture that has been' recorded in the literature was made by 

 Beyerinck (1890). He boiled some ditch water with 10 per cent 

 gelatin, allowed it to cool, and then mixed with it a drop of water 

 containing numerous unicellular green algae. Small algal colonies 



