Joseph began to learn botany at his wife's prodding. She learned the study of flora after she gave up her dreams of being a musician. In 1915, while living in a mission camp and continuing to preach to the natives, Joseph and Mary made their first study together at Mount Kinabalu in North Borneo. In a period of six weeks they found and documented 101 new species of plants. In July 1931 he and his wife moved onward, leaving Luzon and the Philippines for Borneo again. There they began a plant collecting expedition which was later commissioned by the British Museum.