BSIP completed twenty five years of its successful existence in September 1971. To mark the occasion an International Palaeobotanical Conference was held from 5th to 11th December 1971. The scientific program consisted of 6 symposia, 9 sessions of contributed papers and 5 special lectures. 200 delegates including 11 participants from abroad representing various botanical and geological organizations, universities and institutions attended the conference.

During the Silver Jubilee celebration a series of lectures were delivered and Ist Silver Jubilee Commemoration lecture was delivered by K. Faegri on "Major ecological steps in the development of plant  life".