In view of the limited time that will be available for discussions in Nancy, this addendum has been prepared. Arising from the previous collaborative work and Mr Bravery’s visit to most of the co-operating Institutes, a scheme of work entailing tests carried out 1) by a technique chosen by individual Institutes; 2) by an agreed standardised technique would appear to be the best approach. A complete programme of work would embrace a) agar tests; b) soil tests -in sterile soil -in unsterile soil. Clearly allocation of priorities eg to concentrate in the first place on tests in unsterile soil, will be needed. To facilitate discussion on a standardised technique, possible methods for conduct of both agar and soil tests are included in appendix I and II respectively. Full details of practical procedures and methods of computing results have not been included.