On March 1st, 1971, Dr. Hermann Otto Sleumer, senior staff member of the Rijksherbarium, retired on reaching the age of 65 years. I have expressly omitted to say ‘from active service’, because his work has gone on uninterruptedly and he even had objections against spending one afternoon, on Febr. 26th, to celebrate this occasion with speeches and a reception in his honour. Also Mrs. Sleumer found it quite unnecessary and did not anticipate it with pleasure, but afterwards both told us that they had enjoyed it immensely. The story of the life of a scientist is to me always fascinating if it provides, apart from the plain facts of education, career, and bibliography, an insight also into the motives of his personality, the opportunities life offered to him, the challenges he had to meet, and the way he solved them or came to decisions. Too often the incentives and personal notes fail to come to the fore and consequently such so-called biographies fall short of a true life sketch.