12 CULTURE METHODS AND TECHNIQUE 



Isolation by means of solid media. Credit for the sudden perfec- 

 tion of isolation methods is due to Robert Koch. He had watched 

 to good advantage the difficulties in the way of securing isolated 

 colonies of bacteria on potatoes, or by the older methods, and in 

 search of a more desirable medium, he began experiments in a 

 wholly new field. The outcome of his researches was the substi- 

 tution for potatoes of a substance which would have both liquid and 

 solid properties. This substance he found first in gelatin and later 

 in agar agar. Either of these could be employed in his simple and 

 efficient poured-plate isolation method. The results of those studies 

 have given us a powerful equipment for the study of the fungi as 

 well as the bacteria. The substitution of Petri dishes for plates, 

 and many refinements in the way of sterilization apparatus followed 

 promptly. 



Mycological advances. Meanwhile valuable contributions had 

 been made by De Bary, Brefeld, and others, serving to stimulate 

 research along purely mycological lines. The employment of syn- 

 thesized media, improvements in the general methods of making 

 nutrient media, and the use of diverse plant products have brought 

 into the work, on the one hand, the development of definite stand- 

 ards, and, on the other, the possibility of cultivating forms once 

 prevailingly thought to be specialized parasites. The recent devel- 

 opment and application of culture methods from the phytopatho- 

 logical standpoint has been such as greatly to stimulate renewed 

 interest in systematic mycology, and the physiological aspect of the 

 work has been notably advanced. In fact, the physiological studies 

 of the past ten years have been to a very commendable degree 

 studies in the physiology of the fungi. The simplicity of form, the 

 great variety in species and in habitats, the readiness of growth in 

 pure culture, and the rapid response to stimuli all unite to make 

 these plants favorable material for investigation and demonstration. 



II. CLEANING GLASSWARE 



Even for ordinary purposes in culture work glassware should be 

 thoroughly cleaned. Any reagents which will conveniently accom- 

 plish the purpose may be used, but the general methods followed 

 in bacteriological laboratories are to be advised. Special methods 

 will be necessary in certain cases and here one's knowledge of 



