CONTRIBUTIONS FROM THE WISLEY LABORATORY. 



368 



Great Britain and Ireland and to be widely distributed, and that it has 

 been reported to the Board chiefly from those parts of Great Britain 

 ui which " black scab " is present or is suspected; it is further stated 

 that certain knobs and swellings which frequently appear in tubers 

 affected with ' ' corky scab ' ' have been mistaken for the symptoms 

 of "black scab," and they have generally been reported as such. 

 My own experience is that the symptoms of the two diseases have been 

 and are very frequently confused, and this is due to a great extent to 

 the absence of sufficiently detailed information concerning potato 

 canker to enable a fair comparison to be made. 



This paper is divided into sections, relating to:~ 



1. The histoiy of Chryso'plilyctis enllohiotica, Schilb., the organism 

 causing " potato tumour." 



2. The history of Spongospora solani, Brunch., the organism 

 causing ' ' potato canker. 



3. A comparative account of the symptoms of the two diseases. 



4. The supposed earlier descriptions of S-pongospora. 



5. Field observations. 



1. Chrysophlyctis endobiotica. 



Clirysophlyctis endobiotica. K. Schilberszky, m Ber. der 



Deutsch. Bot. Gesell. xvi. p. 36 (1896). 

 Oedomyces leproides (Trabut). G. Massee, in Jour. Bd. Agric. 



Eng. ix. p. 307 (1902). 

 Synchytri'iim endohioticuni. J. Percival, in Geutr. jilr Bakt., 



bd. 25, p. 439 (1910). 

 Synchytrium solani. G. Massee, m Diseases of Cultivated Plants 



and Trees, p. 98 and p. 573 (1910). 



On July 22, 1902, some diseased tubers sent by Mr. Eckford 

 were exhibited before the Scientific Committee of the Eoyal Horti- 

 cultural Society. These were referred by the Committee to M. C. 

 Cooke to report upon. His report was furnished at the next meeting 

 on August 5.'^ He made the following statement: "The cells 

 of the diseased tissue contained subglobose brown bodies (about 

 25 /li X 20 fi) on hyaline pedicels resembling much the gonidia of 

 Pythium. This parasite being quite new to me, and unnoticed in any 

 work to which I had reference, I consulted Mr. Massee, who had made 

 a special study of this group, and he at once informed me that the 

 same disease appeared last year near Birkenhead, where it completely 

 destroyed a field of potatos, and that it evidently was allied to Pythiutn, 

 and had been found in Germany, and called Chrysophlyctis endobiotica 

 (Schilberszky, Ber. Deuts. Bot. Gesell. p. 36, 1896). As far as we 

 j have been able to discover, this genus has never been described, but 

 seems to be a close ally of Pythium, and very similar to the fuugus 



* M. C. Cooke, Jour. B.H.S., xxvii. (1902), p. cxliv. 



