293 



*- 



fungus obtained. Care was taken only to use those spots which 

 close examination showed had the skin unbroken. 



The first attempts to grow the fungus were made in March, 

 1918, on fresh potato agar, when it fructified but the growth was 

 exceedingly slow. Attempts made more recently to grow it on 

 potato agar have, however, been much more successful. It is 

 probable that the temperature factor plays an important part in 

 the growth of the fungus and accounted in a large measute for 

 the slow growth first obtained in cultures. 



Inoculations were made with a large variety of other media, 

 including oatmeal agar and gelatine, bean agar, soil-extract agar, 

 bread, meat-extract agar and gelatine, also liquid extracts of 

 potato and meat, when it was found that the fungus was more 

 or less indilferent to the kind of medium employed, 

 media, oatmeal agar gave the best growth, and on bread slants, 

 although much mycelium has developed, very few spores were 

 formed. The growth was more rapid on liquid cultures, but the 

 most recent inoculations showed that the media on which the 

 fungus grows best are cooked vegetable-tissues, such as potato, 

 carrot, parsnip, etc. On these the growth is not only of a more 

 luxuriant type, but exceedingly rapid — an area covered on these 

 media in a week being equivalent to a month's growth on agar 

 media. In the case of the series of " o _ 



ascertain whether the fungus would grow parasitically, but as 

 the following table shows, such was not the case. 



Of the agar 



cooked vegetable slants 

 parallel cultures of uncooked slants were made in order 



Sterilised media 

 (saprophytic growth) 



Uncooked media 

 (Parasitic growth) 



» • w 



Apple ... 



Artichoke, Jerusalem 

 Beet ... 



Carrot 



Parsnip 



Potato 



• « • 



Very slight growth 

 Good growth ... 

 Moderate growth 

 Good growth ... 

 Moderate growth 

 Good growth ... 



t • ■ 



• ■ t 



* * 



No growth 



»> 



»» 



if 



t» 



5J 



'• 



J* 



»S 



Very poor growth 



readiness with winch the fungus grows under saprophytic 

 conditions and the very slight parasitism which it displays on 



the potato tuber suggest 



fung 



a saprophyte, probably living on dead organic matter in those 

 soils rich in humus, on land heavily manured with farmyard or 



other organic manures. 



It has already been suggested that temperature is an important 

 factor in the growth of the fungus, and although it has not been 

 possible as yet to go into this matter in any detail, a few observa- 



tions have been made. Parallel cultures were inocul 



temperature (U 



C.), 



placed immediately (1) in normal room 



(2) in an incubator at approximately 24° C, and (3) at a tempera- 

 ture just below freezing point. At the end of a week there was 

 no growth in any of the tubes except in that kept at room 

 temperature. The tube kept at 24° C. and also that kept below 



