[2] In 1937 Willis joined the National Herbarium of Victoria and commenced studies at the University of Melbourne, graduating with a Bachelor of Science (Honours) in 1940.
[2] He became the first editor of Muelleria, the peer-reviewed scientific journal published by the Royal Botanic Gardens Victoria, editing the first three issues.
Willis also ventured to Western Australia as a member of the Sir Russell Grimwade Expedition in 1947, and to the Recherche Archipelago in 1950.
Willis was appointed a Member of the Order of Australia in the 1995 Queen's Birthday Honours for "service to botany, particularly in the field of Australian flora".
[8] In 2000, the Gladstone Bag belonging to Willis used to collect specimens on his many field expeditions was uncovered in extraordinary circumstances.