362 



Profs. Percy Frankland and Marshall Ward. 



Note particularly the fall in the curve at 4.50 to 5.1, when the 

 temperature began to fall ; it shows how very sensitive to tempera- 

 ture-changes the growing filaments are, and how extremely difficult it 

 is to eliminate this source of error. 



Spores sown at 8.30 A.M., July 7, were kept at 22 C. in dark till 

 2.45 P.M., and then the selected rodlets treated exactly alike at the 

 north window. Dull, cloudy, and eventually raining. 



Lengths. 



I now pass to the comparative cultures in light and dark, premising 

 that eich pair of cultures must be compared by itself, the difficulties 

 of observation and preparation being so great that one cannot possibly 

 push the method further. 



As before, I begin with the exposures of ungerminated spores, and 

 pass afterwards to exposures of already germinated rodlets and fila- 

 ments in active growth. 



On June 23 spores were sown in dilute broth-gelatine at 10 A.M., 

 and exposed at once. The quartz cells, shades, and screens as before. 

 The temperature at 10.30 was 19-5, slowly falling at the open 

 window to 19 C. at 12 noon, and exactly alike under both screens. 

 The sky was overcast, with traces of hazy blue now and again, and a 

 cool wind was blowing ; no rain fell, but the afternoon was very dull. 

 The following are the results, germination having begun soon after 

 12 noon. 



