212 CULTURE METHODS 



calcium phosphate which is left in the fluid. This makes a .7% solution 

 of the salts, which is too strong for general purposes. It is better diluted 

 with an equal quantity of water (making a .35% solution), or, for delicate 

 algEe, with two liters of water (making what is approximately a .2% solu- 

 tion of the salts). Algre are placed directly in this culture solution, 

 and many of them do well in it. 



B. Jf core's solution. Moore reports that the following solution (which is 

 a modification of one of Beyerinck's) is much more satisfactory than 



that of Knop : 



ammonium nitrate .5 gram 



potassium phosphate .2 gram 



magnesium sulphate .2 gram 



calcium chloride .1 gram 



iron sulphate trace 



These salts are dissolved in a liter of water. For blue-green algae the 

 amount of ammonium nitrate should be doubled, and 1-2% of glucose 

 may be added with benefit. 



C. Cane sugar. A 2-4% solution of cane sugar is an important fluid, since 

 some algae — as Vaucheria, Hydrodictyon, and Spirogyra — will gener- 

 ally fruit after a few days when transferred to it from pond water or 

 cultures solutions and exposed to bright light or moderate sunshine. 



201. Cultures on agar-agar. Pure cultures of unicellular algae may be grown 

 and isolated on agar-agar mixed with a nutrient solution. Moore recom- 

 mends his modified Beyerinck's solution (Sec. 200, B), with double the amount 

 of ammonium nitrate and 2% of glucose. To a liter of this solution (heated to 

 boiling) 5 grams of agar is added, and after its liquefaction the fluid is poured 

 into small Erlenmeyer flasks of 100 co. capacity, or other small dishes which 

 may be tightly covered ; on cooling, the liquid will stiffen to a moist jelly. 

 Pure cultures may be easily established in such vessels, and if protected 

 from drying will flourish for years. 



THE CULTUEE OF FUNGI 



202. Cultures in moist chambers. Fungi will grow in abundance upon a 

 great variety of substances when kept damp in moist chambers. The most 

 convenient form of a large moist chamber is a rather low bell jar five to 

 six inches high, set in a dish of water. The substance is placed on some sup- 

 port, such as a zinc rack, so that it is raised above the surface of the water, 

 the evaporation of which keeps the air in the interior of the bell jar moist. 

 It is well also to line the interior of the bell jar with moist filter paper in con- 

 tact with the water below. Cultures upon large pieces of bread and cheese are 



