L.4B0RAT0RY AND TEACHING METHODS 639 



Notes. — ^The morphologic characters shall be determined and described from 

 growths obtained upon at least one solid medium (nutrient agar) and in at least 

 one liquid medium (nutrient broth). Growths at 37°C. shall be in general not older 

 than twenty-four to forty-eight hours, and growths at 2o°C. not older than forty- 

 eight to seventy-two hours. To secure uniformity in cultures, in all cases prelimi- 

 nary cultivation shall be practised as described in the revised Report of the Com- 

 mittee on Standard Methods of the Laboratory Section of the American Public 

 Health Association, 1905. 



The observation of cultural and biochemic features shall cover a period of at 

 least fifteen days and frequently longer, and shall be made according to the revised 

 standard methods above referred to. All media shall be made according to the same 

 standard methods. 



Gelatin stab cultures shall be held for si.x; weeks to determine liquefaction. 



Ammonia and indol tests shall be made at the end of tenth day, nitrite tests at 

 end of fifth day. 



n 



Titrate with — NaOH, using phenolphthalein as an indicator; make titrations 



at times from blank. The difference gives the amount of acid produced. 



The titration should be done after boiling to drive off any CO2 present in the 

 culture. 



Generic nomenclature shall begin with the year 1872 (Cohn's first important 

 paper). Species nomenclature shall begin with the year 1880 (Koch's discovery of 

 the poured plate method for the separation of organisms). 



Chromogenesis shall be recorded in standard color terms. 



LESSON 29 



DIRECTIONS FOR THE STUDY OF PATHOGENIC FUNGI 



The directions given below for the study of the fungi which cause diseases in 

 plants have been made as general as possible so that the student will find enough 

 flexibility in the outline that it may be applied to description of any of the patho- 

 genic fungous organisms which may be presented to him in his laboratory or field 

 work. The use of such directions is in line with the best teaching methods in this 

 country at the present time. The student is given the diseased organ or plant for 

 study and by following the outline an acquaintance is obtained not only with the 

 diseased conditions of the host, but with the morphologic character of the fungus as 

 well. Some teachers emphasize the importance of getting away from the study of 

 systematic details and concentrating the attention of the members of the class in 

 mycology upon the plant diseases on the basis of the pathologic phenomena exhibited. 

 Perhaps this is the best plan with advanced students, who have some knowledge 

 of the morphology and classification of the fungi, a knowledge which should precede, 

 it seems to the writer, a more detailed study of these interesting plants. It is recom- 

 mended to the teacher that this outline be used closely in connection with the study 

 of the diseases described in part III of this book. The teacher, of course, is at liberty 

 to select other forms for study as the geographic locality may afford. The following 



