H. WORMALD 37 



causing great damage; it is attributed to Sclerotinia {Monilia) fructigena 

 but is probably caused by M. cinerea. 



As there is still some confusion in respect to the nomenclature of the 

 Monilias parasitic on fruit trees, and since the work recorded in the 

 present paper affords evidence of the occurrence of biologic forms of 

 M. cinerea, it is desirable that a comparison be made of the forms of 

 Monilia from various fruit-growing localities; the writer therefore would 

 be glad to receive specimens of affected fruit or branches from other 

 counties that the fungus present on the diseased material may be com- 

 pared with those strains obtained from trees in Kent. 



III. INOCULATION EXPERIMENTS. 



During the spring and summer of 1917 inoculation experiments were 

 carried out, using pure cultures of a strain of Monilia cinerea obtained 

 from a dead twig bearing Monilia pustules, with the object of acquiring 

 further knowledge relative to the mode of parasitism of the fungus, and 

 the extent of the injury caused by it. Several strains had been isolated 

 during the summer of 191G and grown as pure cultures, but, as some 

 organisms are known to become less virulent after continued growth on 

 artificial media, it was thought desirable to start cultures of a strain 

 isolated during the same season as that in which the inoculations were 

 to be made. Since there w^as also the possibility of the occurrence of 

 variation in the virulency of different strains of Monilia cinerea, par- 

 ticularly as it had been found that cultural variations were to be detected 

 among the strains, it was decided to work throughout with one strain, 

 known to originate in a single conidium and actually obtained from a 

 " withered tip " of a plum tree. 



The method adopted in isolating the strain used for the inoculation 

 experiments was as follows : 



Towards the end of March 1917, a twig, which had been killed during 

 the previous summer and which bore a number of the grey pustules 

 typical of the fungus, was removed from the tree and placed in a moist 

 chamber. In 48 hours the pustules had become very pulverulent and 

 conidia were removed by means of a sterile needle and placed in sterile 

 distilled water in a watch glass; the conidia floated on the surface and 

 drops of the water were transferred with a platinum wire loop to an agar 

 plate. Some of the drops contained isolated spores and these could be 

 examined under the microscope through the bottom of ttie piai(\ Aftftr 



