Theo Arts was born in Aalst, Belgium on 2 January 1942. He was one of the first and most active members of the 'Vlaamse Werkgroep Bryologie' (1978). He was also president of this Flemish bryological working group from 1989 to 1994. His special interest was in propaguliferous mosses, especially those with rhizoidgemmae; almost half of his publications are dedicated to this group.
He traveled much in the tropics and, as a collaborator of the Garden, he planned a flora of the mosses of Réunion. He died suddenly on 11 October 2000. His large herbarium with the documentation has been bequeathed to the Garden.