550 Scientific Proceedings^ Royal Duhlin Society. 



medium was used in a liquid form, aud heuce a considerable number of 

 cultures were made in liquid-oat-extract of varying degrees of concentration. 

 The tubes containing the liquids were inoculated with mycelium bearing no 

 sexual organs or conidia, from pure cultures, on ordinary wort gelatine. The 

 result of all the cultures was that the amount of growth varied directly with 

 the concentration of the liquid in food materials, being practically nil in the 

 extremely dilute, and greatest in the undiluted, extract ; but neither conidia 

 nor sexual organs were produced in any single instance. 



If small pieces of recently attacked tissue are removed from an affected 

 tuber with aseptic precautions, and are placed in sterilized rain-iuatcr, filtered 

 hog-water, or watery [extract of hog-soil, the mycelium grows out from the 

 introduced tissue in the course of three or four days, at room-temperature, and 

 can be seen with the unaided eye adhering to them like seaweed to submerged 

 stones. This growth does not become so luxuriant as that developed in 

 nutritive solutions such as oat-extract ; but examination with the microscope 

 after the lapse of about a week or more reveals the presence of both sexual 

 organs and conidia. The sexual organs are most abundant in the bog-soil 

 extract and in the bog-water, while the conidia are most abundant in the 

 rain-water, and least in the bog-soil extract. The oospores appear to take up 

 some of the colouring-matter from the bog-water, and become dark brown. 

 In a somewhat similar fashion both sexual organs and conidia are produced 

 when purely vegetative mycelium, together with a little adhering medium 

 (ordinary, slightly acid wort gelatine), is introduced into sterile bog-soil 

 extract, a fair amount of fresh mycelial growth being developed. 



Attempts were made to cultivate the fungus as a saprophyte on bog-soil 

 itself. For this purpose the soil was first air-dried, then sifted through a fine 

 sieve, moistened with water, and filled into Petri dishes until tliey were 

 about half full. Tliese were then heated in a steam sterilizer on three 

 successive days. They were " seeded " by planting in the centre of each 

 either a small piece of diseased tissue from a tuber, or a small portion of 

 mycelium from a pure culture on ordinary wort gelatine. After about a week 

 or ten days at room-temperature a very slight superficial growth could be seen 

 radiating out from the piece of inoculating material for a distance of about 

 5 mm. On this superficial growth microscopic examination revealed the 

 presence of abundant sexual organs, but no conidia. 



The feeble amount of development suggests that the fungus cannot 

 utilize the bog-soil itself as a medium for growth, but what new growth 

 does occur is probably made at the expense of the food material present 

 along with the inoculating material. It would, however, seem that, provided 

 that the fungus were already established upon some favourable medium in 



