GROWTH 31 



trated by Fig. 4, where two methods of measuring the amount of growth 

 of Ceratostomella fimbriata were used. This figure demonstrates that the 

 diameter of a colony may be a very poor measure of the amount of growth. 

 Fries (1943) grew Ophiostoma {Ceratostomella) ulmi on agar medium and 

 measured the radii of the colonies and also w^eighed the mycelium after 

 removing the agar. After 5 days the average radius of cultures without 

 pyridoxine was 16.3 mm., while the average radius of cultures receiving 

 pyridoxine was 12.3 mm; the weights of mycelium produced under these 

 two conditions were 5.2 and 18.1 mg., respectively. It is clear from these 

 examples that different methods of measuring growth do not always give 

 comparable results. Before valid conclusions can be reached, it is neces- 

 sary to use valid methods of measuring the quantities involved. 



METHODS OF PRESENTING RESULTS 



The data obtained in a well-planned and carefully executed experiment 

 have value in themselves, but more frequently data are a means to an end. 

 Experimental data form the basis upon which conclusions are reached and 

 serve as a guide to further investigation. A conclusion is sound only if 

 the data are sound. To be of greatest value, data must be presented in an 

 understandable manner. Extensive data may be presented either as 

 tables or graphs; each method has certain advantages. 



Tables. The utility and conciseness of tables make them desirable for 

 many purposes. Tables are especially suitable in comparing the amount 

 of growth (or any other function under study) of a number of fungi under 

 standard conditions or under a number of conditions. They give the 

 reader the same basic and fundamental information available to the 

 original investigator. The utility of such information can be appreciated 

 only when one attempts to assess the reports in the literature. 



Derived data, such as ratios or percentages, may be needed for the pur- 

 poses of interpretation and study, and as such they are entirely proper. 

 However, the original data from which the derived data were calculated 

 should always be published. The original data frequently have values 

 which are not perceived or considered by the original investigator. 

 Derived data as such afford no clue as to the original magnitudes. 

 Without the original data no comparison can be made with other experi- 

 ments, whether in the same or other laboratories. The usefulness of 

 many publications is severely limited because the author presented only 

 ratios or percentages instead of the original data. If a datum represents 

 an average value, the number of determinations upon which it is based 

 should be stated. It is desirable to indicate the range of variation among 

 replicates, or the standard deviation should be given if the number of 

 observations is large. 



