230 Infestation of Fungus Cultures by Mites 



was no recovery of mites or hatching out of eggs. They were then sub- 

 cultured on Czapek's agar and all the subcultures grew and were ap- 

 parently unaffected by the Pyridine. The six cultures of Mucor were, 

 however, contaminated with Penicillium. A possible explanation of this 

 seems to be that the mite Glyciphagus, present only in these tubes, has 

 long hairs capable of carrying Penicillium spores. The cultures treated 

 were of species isolated from the soil and were as follows: 



Mucor hiemalis (Wehmer), Botrytis pyramidalis (Sacc), Johnson, 

 Hormodendrum cladosporioides (Fres.), Sacc, Gliocladium penicillioides 

 Corda (Icon.), Stachybotrys alternans Bonord., Monosporium sp., Fu- 

 sarium, sp. 1, Fusarium, sp. 2, Penicillium, sp. 1, Penicillium, sp. 2. 



Nine other unidentified species including one of the Sphaeropsidales 

 and a Dematiate form were also treated, the total number of cultures 

 being 78. Since this experiment the method of treatment has been used 

 a number of times and has been successful with one possible exception. 

 In the latter case three cultures which had been treated were found some 

 months later to be infected, but as they were among other newly infected 

 cultures it was impossible to tell whether this was due to the failure of the 

 original treatment or to re-infection. It was decided, in view of these 

 results, to carry out a few quantitative experiments on the toxic effect 

 (if any) of Pyridine to some common fungus, in order to ascertain how 

 far this treatment could be carried with safety. The fungus chosen was 

 Aspergillus niger, since work on the effect of Pyridine and various 

 organic bases on this organism had been carried out by Brenner (5) and 

 Lutz{6). 



Into each of a series of conical flasks of 500 c.c. capacity, 200 c.c. of 

 a suitable liquid medium was introduced, and sterilised. Gradually 

 increasing amounts of pure Pyridine were added, and the flasks inocu- 

 lated with 5 c.c. spore suspension. After a period the cultures were 

 filtered, thoroughly washed by decantation, dried and weighed. After 

 some preliminary experiments Coons' solution containing double the 

 amounts of all the ingredients was decided upon as giving in a reasonable 

 time a yield of a suitable amount for both washing and weighing pur- 

 poses^. 



The most rapid and efi&cient filter was a Gooch crucible used with a 

 pad of cotton-wool and under a not too high vacuum. The Gooch 



