In the 1890s, a growing number of Crépin’s correspondents were waiting impatiently for his rose monograph.
In response to constant inquiries about the publication date, a subscription form was finally circulated, in which the publication of Prodrome de la Monographie des Roses was announced for the winter of 1894-95. However, nothing came of this announcement.
During the final years of his career, new and seemingly unanswerable questions kept popping up in Crépin’s head. Applying new approaches (including some crude statistics) and asking for yet more collections to be sent in by his correspondents, the rhodologist covered sheets of paper with nagging questions to which there were no easy answers. The completion of his monograph became a chimera.
In 1895, the ambitious French botanist Paul Evariste Parmentier (1860-1941) was convinced he could solve the old problem of the classification of the genus Rosa by applying the most advanced anatomical and histological analysis to the study of the microscopic structure of tissues.
To help bring this task to a successful conclusion, he sought the collaboration of Crépin. Before long, however, tensions mounted. Crépin felt insufficiently appreciated by Parmentier, 30 years his junior. Crépin thought that Parmentier minimised the importance of morphology (the study of the shape and organisation of the parts of an organism) upon which his lifelong phytographic work always had relied. For his part, Parmentier bluntly told the ageing expert rhodologist that the old approaches were outdated and that new techniques were required to arrive at a natural classification of the genus Rosa.
The intellectual clash between Parmentier and Crépin pitted two egos and two generations of researchers against each other.
It exhausted Crépin compounding the doubts that had been building up in previous years. It brought an end to his publications. A few years later, failing health forced him to resign as secretary of the Société royale de Botanique de Belgique and as director of the State Botanic Garden.
François Crépin died in 1903, leaving a wealth of materials available for the completion of his monograph of Rosa which he himself had been unable to complete. Today, his heritage – including the herbarium of roses kept at Meise Botanic Garden – is still held in high esteem and offers great opportunities for renewed study involving 21st-century molecular techniques. However, a universally-endorsed classification of the genus Rosa is still missing. It is still an ongoing project, riven with obviously thorny questions.