76 Plant Tissue Culture 



flamed (Saeger, 1933, 261). Cotton plugs char, 

 and bits of charred cotton falling into flasks of 

 nutrient may vitiate the results of nutrition 

 experiments. Cotton itself contains significant 

 quantities of thiamin (Schopfer et Rytz, 1937, 

 226). With rare exceptions, the custom of flam- 

 ing the mouths of tubes and plugs is a pernicious 

 hocus-pocus. Flasks which are properly handled 

 and plugged and are capped to keep out dust and 

 water of condensation will remain sterile for 

 months without flaming. Instruments can be ade- 

 quately sterilized in boiling water. If needles for 

 bacteriological studies must be flamed, this can be 

 done quite satisfactorily in a small alcohol flame 

 without the hazards involved in the use of gas. 

 The use of gas around a plant tissue culture labo- 

 ratory should be reduced to a minimum. 



The culture rooms. The details of culture 

 rooms, laboratory, and office will, of course, be 

 modified to meet the needs and facilities of indi- 

 vidual workers. Facilities for accurate control 

 of temperature, illumination, and humidity, and 

 experimental comparison of different levels of 

 these factors are desirable. Since plant tissue 

 cultures are extremely sensitive to temperature 

 fluctuations (White, 1932, 63, 1937, 265, 266) and 

 have an optimum temperature only slightly above 

 room temperature (about 27°-30° C), it is impor- 



