Pethvbkidge & Lapfekty — Disease of Tomato and other Plants. 495 



Nicotiana affinis. The fungus, however, was found capable of attacking Asters, 

 Petunias, "Wallflowers (Cheiranthus), Gilia tricolor, and seedlings of Beech 

 (Fagus sylvatica), producing in all these plants symptoms very similar to those 

 observed in naturally affected tomato plants. In some of these, as will be 

 seen from a later section of this paper, the same disease occurs naturally. 



When inoculated into living potato-tubers, the fungus causes a rot very 

 similar to the "pink rot" caused by PliytopMliora erythroseptica. When portions 

 of the rotted tissue were placed in sterile water, sporangia were developed 

 rather sparingly, but no sexual organs were formed. Under these conditions, 

 P. erythroseptica produces an abundant crop of sexual organs and sporangia. 



The fungus has been found to be actively parasitic to apples and white 

 turnips. It also slowly attacks mangels and swedes, but does not attack 

 carrots or parsnips. In all cases inoculation was carried out through wounds. 



V. — Development of the Fungus in Pure Cultures. 



The fungus was found to grow with more or less vegetative luxuriance on 

 a considerable number of different agar and gelatine media, of which sixteen 

 kinds were tried, as well as on sterilized portions of various stems, fruits, &c. 

 It did not cause the liquefaction of gelatine media. The kind of mycelium 

 developed is illustrated in fig. 1, PL XLVII. 



The striking point about all these cultures was the reluctance of the 

 fungus to produce either asexual or sexual reproductive organs. In a few 

 cases, as, for instance, on sterile soil and on oat-extract-agar, there was a 

 meagre development of sporangia. This also occurred when a small portion 

 of a culture on Quaker Oat-agar was transferred to sterile tap-water or bog- 

 soil-extract. In other eases, the addition of sterile water to tubes containina; 

 slanted cultures on various media resulted in a good development of mycelium 

 in the water, but reproductive organs did not arise. 



In the cases mentioned above in which sporangia were formed, they exactly 

 resembled those already described both in shape and size as well as in method 

 of zoospore production, and they need not, therefore, be described again. 



At this point in our work the study of the fungus had to be suspended 

 temporarily, owing to the pressure of urgent work more directly connected 

 with food-production ; and a period elapsed during which the only thing done 

 was to make transfers of the cultures every few weeks in order to keep the 

 fungus alive and in good order until the study of it could be resumed. This 

 period lasted from January to October. At the beginning of it the stock 

 cultures were on Quaker Oat-agar. and this medium alone was used for the 

 subsequent transfers. The whole series of original stocks and intermediate 

 transfers was kept for future microscopical examination. 



SCIENT. PROC. R.D.S., VOL. XV.. NO. XXXV. 4 H 



