. Fungous diseases of plants, with chapters on physiology, culture methods and technique . to stimuli all unite to makethese plants favorable material for investigation and demonstration. II. CLEANING GLASSWARE Even for ordinary purposes in culture work glassware should bethoroughly cleaned. Any reagents which will conveniently accom-plish the purpose may be used, but the general methods followedin bacteriological laboratories are to be advised. Special methodswill be necessary in certain cases and here ones knowledge of ISOLATION AND PURE-CULTURE METHODS 13 chemistry must direct. Ordinarily i
. Fungous diseases of plants, with chapters on physiology, culture methods and technique . to stimuli all unite to makethese plants favorable material for investigation and demonstration. II. CLEANING GLASSWARE Even for ordinary purposes in culture work glassware should bethoroughly cleaned. Any reagents which will conveniently accom-plish the purpose may be used, but the general methods followedin bacteriological laboratories are to be advised. Special methodswill be necessary in certain cases and here ones knowledge of ISOLATION AND PURE-CULTURE METHODS 13 chemistry must direct. Ordinarily it is not enough to depend uponhot water and soap in cleaning glass vessels. Petri dishes, testtubes, etc., may be boiled for a short time prior to cleaning, and ifgrease is present, a small quantity of potash lye (about 30 gramsper liter) may be added. If the glassware is immersed in water, aporcelain-lined vessel should be used, and the latter may be placedover the flame or in the steam sterilizer. Commercial hydrochloricacid is convenient in many cases for general use. A chromic acid. Fig. 2. Some Chief Types of Glassware required in Student CultureWork. (Photograph by Geo. M. Reed) cleaning mixture has also become quite generally adopted and givesexcellent results. This mixture may be made sufficiently strong forordinary purposes by dissolving 100 grams of potassium dichromatein 1000 cc. of hot water, then when the salt is all dissolved andthe liquid cool, pour into it about 500 cc. of strong sulfuric acid,stirring constantly. This liquid should be stored in large-mouthed,glass-stoppered bottles, and used with care. It may be used repeat-edly. When employed, it may act for from ten minutes to twenty-four hours, and it may be followed by water, or soap and water,etc. This mixture is not convenient to handle but is ver) tubes. Ordinarily these should be cleaned with hot water,soap and a test tube brush ; and this cleaning may be preceded or 14 CULTURE METHODS AN
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