CONTRIBUTIONS FROM THE WISLEY LABORATORY. 



547 



later'^" he transferred Sorokin's fungus to the genus Clasterosporium, 

 caUing it C. fragile, although he remarks " An Toruhie affinis? Cert.e 

 longius distat ab Hehninthosporis. " 



The name of the fungus involved is therefore Thielavia basicola 

 Zopf. Torula basicola Berk, and Br., Hehninthosporiiim fragile 

 Sorok., and Clasterosporium fragile (Sorok.) Sacc. are synonyms. 



Berkeley was in some doubt as to whether the fungus was a sapro- 

 phyte or a parasite, for he saysf : "It is either destructive of the 

 plant on which it grows, or is developed on it in consequence of pre- 

 vious disease," and the doubt he felt is certainly emphasized by the 

 fact that the fungus has been found on a large number of plants 

 belonging to many different and quite distantly related families. 



Thus Zopf found his examples on the roots of Senecio elegans, 

 in Berlin, and subsequently wrote a paper describing its attack 

 upon Lupines :[: (Lupinus angustif alius, L. albus, and L. tJiermis); 

 he also found it on Trigonella coerulea, Onobrychis Cristagalli, 

 Pisum sativum, &c. Sorokin's specimens came from dead roots of 

 horseradish' {CocJilearia Ariiioracia) in Eussia. Selby found it on 

 Begonia rubra in greenhouses in Ohio; J. J. M. Van Hook on 

 Gingseng [Aralia quinquefolia) ; Thaxter (the first to find it in America 

 in 1891) on violets ; many observers in America and Italy on tobacco ; 

 Bessey on culinary peas in South Carolina (and we have seen 

 many examples of it on the same plant in this country, especially 

 perhaps in 1911, when it was very prevalent), on sugar beets in Utah, 

 and on " various plants " in Florida ; E. F. Smith on cowpea {Vigna) 

 and cotton seedlings ; Sorauer on Cyclamen (on which plant we have 

 also seen it) ; and so on. 



The f,act that Thielavia basicola^ has been found upon such a wide 

 range of plants suggests that possibly this fungus is not a true parasite, 

 for most parasitic fungi are restricted to one plant, or at most to a 

 few plants nearly related; on the other hand, there are some common 

 fungi which appear to be capable of attacking a large number of hosts 

 often widely distinct from one another, and even of growing as sapro- 

 phytes on dead vegetation. Botrytis cinerea belongs to this group, and 

 so does Cladosporiuvi herbaruni. As we have previously shown, § there 

 are strong reasons for suspecting that the last-named fungus is capable 

 of attacking leaves of apples only after they have been weakened from 

 some cause, and it is parasitic upon other plants growing under some- 

 what unhealthy conditions. There has evidently been in the minds of 

 many investigators of diseases where the fungus now under considera- 

 tion has apparently been involved that, in order to permit its attack, 

 the host plant must have been weakened from some cause. 



We have already remarked upon the doubt expressed by Berkeley. 



* P. Saccardo. Sylloye Fungorum, iv. (1886), p. 386. 

 t Berkeley and Broome, I.e., p. 462. 



+ W. Zopf. " Ueber die Wurzelbraune d. Lupinen/' in Zeitschr. f. Pf an- 

 zcnkr. i. p. 72. 



§ F. J. Chittenden. " Contributions from the Wisley Laboratory. I. 

 Apple-leaf spot." (Journal R.H.S., vol. xxxiii. (1908), p. 500. 



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