H. WOJIMAI.D 1S5 



The description given of Monilia laxa of the apricot, as the conidial 

 stage of Sclerotinia laxa applies equally well to the grey Monilia):; ot 

 other fruit. The most striking difference they give is in the size of the 

 conidia, viz. M. cinerea 9-3-14-5 x 6-2-12-4/x, M. laxa 12-4-23-8 x 9-3 

 -lo-Ofx, but this difference is no greater than that shown by the blossom- 

 wilt fungus or the Monilias of plums when growing under such diverse 

 natural conditions as (a) mummified fruit or dead spurs in winter, 

 (6) fresh fruit in summer. 



The present writer is of the opinion from the evidence to hand that 

 the grey Monilias of this country are to be referred to the continental 

 form M. cinerea Bon., the Scleroltnia stage of which has not yet been 

 described, unless indeed it should prove to be identical with Sclerotinia 

 laxa (Ehrenb.) Aderh. et Ruhl. The blossom-wilt fungus must pro- 

 visionally therefore be included under Monilia, cinerea Bon. This 

 species as at present delimited includes at least two forms, one which 

 remains colourless in prune- juice agar cultures, and another which 

 produces zones of an olive green to dark brown colour. The American 

 Brown Rot fungus appears to be a distinct form and it may be necessary 

 to distinguish it specifically from the European species. 



V. Inoculation Experiments with Pure Cultures. 



As observations in the open had indicated that in all probability 

 infection occurred through the open flower, it was necessary that 

 inoculation experiments should be carried out when the trees were in 

 bloom, and the time available under natural conditions was thus limited 

 to about a fortnight in the year. It was decided therefore that a first 

 series of inoculation should be performed under glass in order that any 

 information thus obtained, relative to the mode of infection, could be 

 utilised during the same spring in subsequent experiments in the planta- 

 tion. Another reason for conducting the experiment under these 

 conditions was to eliminate the possibility that the action of frost would 

 modify the course of the experiment. 



Some difficulty was experienced in obtaining conidia in sufficient 

 quantity to ensure successful inoculation. With the object of inducing 

 the fungus to produce conidia readily on a sterilised substratum many 

 culture media were tried, e.g. agar- agar media : 1-5 % agar in an extract 

 of each of the following substances : celery, prunes, French beans, 

 apple twigs, malt culms (also malt culms -f 10 % starch), maize meal, 

 potato. Prune-juice agar containing strips of filter paper was also used. 



