The following comments are designed to aid the instructor in handling and maintaining algal units. They concern the fundamental factors affecting the most frequent studied laboratory cultures.

Shipments of living algae should be opened immediately uoum arrival. If the cultures have been long in transit or exposed to varying conditions of heat and cold, it may be necessary to revitalize the specimens. The lids of the culture jars should be loosened and the specimens kept in subdued light in moderate temperatures of 60-70 degrees F. NOTE: Cultures should be used for classroom study before experimentation and subculturing is attempted.

Equipment: Keeping the units free of contaminating elements is major importance in producing healthy, vialbe cultures. To ensure such an environment, it is necessary to begin (sterile if possible) labware. Containers should be free of all chemical residue and should not have been previously used for fixatives or other toxic materials. Specimens may be cultured in glassware of various sizes. Widemouthed containers with capacities for four to sixteen ounces of medium will prove most convenient in the laboratory.

Medium: In general, pure cultures are difficult and time-consuming to maintain in the laboratory. If culturing is attempted, a soil-water medium is recommended for most fresh-water algae. Soil-water medium can be prepared in large quantities and stored for future use. A sufficient quantity of laboratory stock solution may be obtained by combining eight ounces of rich loam (volume), three grams of calcium carbonate and four liters of distilled water. The stock should be steamed for one hour on two consecutive days and then decanted through several layers of cheesecloth or cotton and stored in cool place. To prevent contamination of the algae, the stock medium should be autoclaved prior to innoculation. Note: For best results, algal cultures should be subcultured every ten to fourteen days. Algae rapidly use the nutrients from small containers and constant revitalization on the medium becomes necessary. Contamination from bacteria and blue green is often a serious problem, and every attempt should be made to keep the cultures attempt.

Temperature: Algal cultures are best maintained between 55-65 degrees F. However, most species will survive at room temperature in the lab. Temperatures should never exceed 75 degrees F.

Light: Subdued light is recommended for most algal cultures. Direct sunlight will raise the temperature of the medium above the level for optimal rates.

pH: Although difficult to control, pH of the culture does play a role in the viability of the medium. Normal ranges of pH are between 7.0 and 7.6. Loss of an entire stock of any one species due to dramatic change in pH may be avoided ny maintaining units of each type.