52 SCIENCE PROGRESS 



later, with corresponding checking of growth. It was found 

 that while growth can take place between the acid and alkali 

 limits of + 30 and — 10 to phenolpthalein, yet reproduction is 

 stopped by a reaction only slightly on the acid side of neutrality. 

 Maize broth is a much better substratum than oat broth, but 

 if the latter be acidified with an acid phosphate, or even hydro- 

 chloric acid, it becomes almost as good a medium as maize. 

 The various laboratory media are rightly condemned as " rather 

 purposeless, clumsy devices in which this organism is overfed." 

 Progress can only be made by the use of synthetic media, and 

 a large number of experiments were made with a medium con- 

 taining in various proportions potassium dihydrogen phosphate, 

 magnesium sulphate, maltose and asparagin. A solution 

 containing these four substances in concentrations of M/100, 

 M/500, M/100, M/500, respectively, was found to be an almost 

 ideal culture medium for the growth and reproduction of this 

 fungus ; the pycnidium production was far higher than in any 

 other medium. In this synthetic medium the inhibition of 

 reproduction as a result of increasing or decreasing the car- 

 bohydrate or asparagin was very marked. 



Light was found to be essential for reproduction, though not 

 for growth. The light need not be continuous, for a short 

 exposure to strong diffuse light of cultures which are ready 

 to produce pycnidia will allow, for a time, the production of 

 these bodies in the dark. Abundant aeration was found to be 

 essential, while transpiration was found to be a factor of only 

 secondary importance. 



The extremely interesting and important observation was 

 made that the stimulus of light could be replaced by a few drops 

 of hydrogen peroxide. This observation was extended, and it 

 was shown that a number of other oxidising agents, such as 

 nitric acid, potassium permanganate, ferric chloride, would 

 produce the same effect and cause the production of pycnidia 

 in the dark. The view is put forward that among the parts 

 of an organism there exists a strong competition for oxygen, 

 and that under conditions which favour growth the available 

 oxygen is all used for ordinary metabolic processes. If the food 

 supply is reduced, as by transfer to media of lower concentra- 

 tions or to distilled water, a " hunger-state " sets in and ordinary 

 respiration is lowered. If the organism is now stimulated by 

 light or by some oxidising agent, oxidation of the richer cell 



