578 Scientific Proceedings^ Royal Dublin Society. 



The aerial mycelium, bearing a prolific crop of eonidia, clothes the whole 

 surface of the slant with a dense growth, whilst submerged mycelium 

 permeates the whole of the substratum. The fungus does not remain alive 

 on this medium for so long a period, however, as on Q,uaker-Oat agar. On 

 the filtered medium the growth is still good, but considerably less luxuriant 

 tlian on the same medium unfiltered. Some thirty or forty cultures were 

 made on these two media, but they did not extend over a period of many 

 months. Both Jones and Clinton found immature sexual organs on Lima 

 Bean agar, but tliey were not to be found in any of our cultures. 



(7) Growth ill Oat-extract Agar. — This medium was prepared from 200 

 grams of very finely ground Quaker Oats, extracted with 1,000 c.c. of cold 

 tap-water. The powdered oats were allowed to stand covered with the water in 

 a corked flask for about five days, a few drops of chloroform having 

 been added to prevent decomposition. Subsequently the whole was well 

 shaken up for some hours on a shaking machine, and then allowed to 

 stand. After sedimentation, the supernatant liquid (about 650 c.c.) was 

 siphoned off and heated in the inner part of a double saucepan until the 

 whole of the chloroform was driven off, and 2 per cent, agar was added. 

 The medium was somewhat turbid, but was not filtered. On subsequent 

 sterilization in the autoclave a curdy precipitate was formed, which settled 

 down as a more or less flocculent mass at the bottom of the tubes. 



P. infestans grows very well on this medium, and soon covers the surface 



-of the slant with a tliick felt of aerial mycelium, on which eonidia are 



developed in abundance. The mycelium also makes extensive submerged 



development. On the whole the growth here is but little less than on 



Quaker-Oat agar, but no sexual organs were ever seen. 



This medium, although slightly turbid, is in thin layers, sufficiently 

 transparent to admit of use with advantage for growing certain species of 

 Phytophthora, either in Petri dishes or in films on the lower surface of a 

 cover-glass in a moist chamber. 



(8) Ot/ier Media.— 1:^0 growth whatever took place on the following 

 media: — Cooked potato ; sterilized bread, carrot and potato-stalks ; potato-stalk 

 extract-agar ; wort-gelatine ; wort-agar ; beef-broth-peptone-gelatine and 

 -agar. 



IV. PuiiE Cultures on Media in which Sexual Organs are formed. 



(1) Clinton''s Oat-jiiice Agar. — The following is the method given by 

 Clinton for preparing this medium : — " Fifty grams of ground oats, such as 

 are ordinarily fed to horses, are stirred into about 300 to 350 c.c. of water, 

 and steam from an autoclave, by means of glass- and rubber-tubing connected 



