173 



ON THE OCCURRENCE IN BRITAIN OF THE CONI- 

 DIAL STAGE OF SCLEROTINIA MESPILI SCHELL 



By H. WORMALD. 



{Soiillt-Easterii Agricultural College, Wgc, Kent.) 



(With Plate XI and 2 Text-figures.) 



While engaged in an investigation of the Brown Rot diseases of fruit 

 trees in this country the writer was informed that for a number of years 

 medlar trees (Mespilus germanica L.) in a cherry orchard near Sitting- 

 bourne, Kent, had suffered from a disease supposed to be a form of 

 Brown Rot. The grower was asked to send specimens to Wye College 

 in the event of the reappearance of the disease and in the middle of 

 April of the present year (1920) medlar shoots were received, the leaves 

 of which showed dark-brown blotches varying in size from about 1 cm. 

 in diameter upwards; in a few cases the whole leaf was affected and 

 completely withered. No organism was visible on the surface of the 

 leaves when received but, on placing the specimens in a moist chamber, 

 grey tufts appeared on the upper surface of one of the dead leaves within 

 four days. Microscopic examination showed the tufts to consist of chains 

 of rather large spherical conidia ; many of the conidia floated free when 

 placed in a drop of water but others were seen to be connected by slender 

 fusoid bodies and it was at once realised that the fungus was the conidia 1 

 stage of one of the Sclerotinias of the S. Linhartiana type, i.e. those in 

 which the conidia become separated by "disjunctors." This term was 

 introduced by Woronin 1 who found and described the development of 

 these bodies in Sclerotinia Vaccinii. 



The diseased leaves emitted a strong sweetish odour which was 

 particularly noticeable on opening the glass case in which such leaves 

 had been confined for two or three days. Healthy leaves kept under 

 similar conditions did not give off this characteristic odour. 



No record could be found of the occurrence of this disease in Britain 2 , 



1 Woronin, M. "Die Sklerotienkrankheit der Vaccinienbeere," Mem. de V 'Acad, de 

 St Petersbourg, Serie 7, T. xxxvi, 1880. 



2 The author is indebted to Miss E. M. Wakefield and Mr J. Ramsbottom for their 

 aid in consulting literature at the Kew Herbarium and at the Natural History Museum 

 respectively. 



Ann. Biol, vii 12 



