444 



Scientific Proceedings, Royal Dublin Society. 



and 3rd, but it was not until three days after this that the last successful 

 infection was found. 



Vitality of conidia in clay, sand and salts. — As the contaminated soil 

 which was the first to fail to produce the disease in the last experiment was 

 in a pot which had been taken indoors during the previous few days, the 

 effect was tried of mixing conidia with a quick-drying medium, such as silver 

 sand, in comparison with clay. As it had been claimed' that the conidia were 

 capable of living over winter in a mixture of calcium sulphate and calcium 

 carbonate, this medium was also tested. The clay, sand, and salts were kept 

 iu Petri dishes. 



The results are shown in Table I. The clay mixture produced blight up 

 to twenty-one days after being made up, the sand mixture up to seven days, 

 and the salts (although they were perfectly dry throughout) up to twelve 

 days. No disease developed from any of the forty-two control inoculations 

 in which clay, sand and salts respectively were used. 



Table I. — Length of life of conidia in clay, silver sand, and salts mixture 



in room. 



(In the case of the numbers expressed as fractions, the denominator represents 

 the number of inoctdations and the numerator the number of infections secured.) 



In this experiment the sand and clay were slightly moist, and as nearly 

 uniformly so to begin with as possible. The sand became noticeably drier 

 during the course of time, and to this fact, possibly, the early death of the 

 fungus is to be attributed. On the other hand, the salts mixture was air-dry 

 to begin with, and it was left in this condition. The surprising length of 

 time which the fungus survived in it appears to be attributable to the fact 



' Griffiths, Chemical News, vol. 53, 1886, p. 255. This experiment was repeated 

 under the conditions given (in a dry incubator at 35° C.) but with an entirely different 

 result from that claimed. 



