Isotype specimens, those that are duplicates of the holotype, were distributed to several herbaria, including those at the University of North Carolina, the New York Botanical Garden, the National Herbarium of New South Wales, and the Queensland Herbarium.
His expertise as a botanist developed following field work in Ontario and Quebec, as well as two years spent in visiting European herbaria and a course of lectures at the Sorbonne, the Jardin des Plantes, and the Muséum national d'Histoire naturelle in Paris, France.
For his publications on Philippine flora, Vidal not only collected specimens, but also studied Malesian flora held in European herbaria, such as the Kew herbarium.