Pethybridge and Murphy — On Phytophthora infestans. 567 



discovery of such structures in P. hifestans when growing on the potato, notably 

 Worthington Q-. Smith' and Smorawski." 



It would serve no useful purpose to refer in detail in the present paper to 

 the controversy raised by Smith's publications ; suffice it to say that his views, 

 owing largely to the critical observations of de Bary, did not meet with 

 anything like general acceptance. Smorawski's work also can scarcely be 

 said to be convincing ; and the bodies described and figured by him as sexual 

 organs do not at all closely resemble the real ones obtained in pure cultures. 



One of us spent a considerable amouut of time a few years ago in searching 

 for possible oospores of P. infestans in the blighted portions of potato-plants. 

 Bodies were found frequently which might have been such structures ; but 

 prolonged attempts at causing them to germinate met with absolutely no 

 success ; consequently their true nature remained undetermined. 



Although only failure has to be recorded as regards the search for oospores 

 along this lino up to the present, success has been attained, as will be seen 

 with pure cultures on certain media. 



That Phytophthora infestans, exquisite parasite though it is often regarded 

 to be, is capable of being grown on a dead substratum has long been known. 

 Possibly Brefeld' was the first to record its growth as a saprophyte when he 

 wrote, in 1883: "TJnter den Peronosporeen habe ich mich auf den am 

 meisten wichtigen und characteristischen Pilz der Kartoiielkrankheit be- 

 sohrankt. — Die Peronospora infestans wuchs in kiinstlicher Ernalirung wie 

 Unkraut, fast so uppig, wie sie auf den Kartoffeln waehst." Von Tubeuf 

 states:^ ^^Phytophthora infestans is more easily reared as a saprophyte [than 

 Exoascus], and occurs in nature as such ; heuce it approaches somewhat 

 towards the hemi-saprophytes." 



Matruchot and Molliard^ claim to have been the first to grow this fungus 

 in pure culture, both on living and non-living substrata, although Hecke" 



' A general account of Worthington Smith's ohservations is to be found in his book, " Diseases of 

 Field and Garden Crops," London, 18S4, particularly in chapter xsxvi. Various earlier articles on the 

 subject were contributed to The Gardeners' Chronicle (and to the Monthly Microscopical Journal, 

 vol. siv, p. HO, and vol. xvi, p. 120) by this author in 1875 and 1S76 ; whUe photographs of the 

 supposed oogonia and antheridia are to be found in Quart. Journ. Micros. Science, vol. xv, N.S., 

 1875, p. 360. 



-Smorawski, J". — Zur Entwiokelungsgeschichte der Phytophthora infestans (Montagne) de By. 

 Inaug. Diss. Berlin, 1890. 



' Brefeld, 0. — Untersuch. aus dem Gesamnitgebiet der Mykologie. Heft v. Leipzig, 1883, p. 9. 



< Von Tubeuf, K., and Wm. G. Smith.— " Diseases of Plants induced by Cryptogamic Parasites," 

 London, 1897, p. 7. 



5 Matruchot, L., et MoUiard, M. — Sur la culture pure du Phytophthora infestans de Bary, agent 

 de la maladie de la pomme de terre. Bull. Soc. Mycol. de France, T. xvi, 1900, p. 209. 



<> Hecke, L. — Untersuchungen iiber Phytophthora infestans de By. als Ursache der Kartoffel- 

 krankheit. Journal fiir Landwirtschaft, Band 46, Heftii, 1898, p. 104. 



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