Even towards the end of his career he was still active, his greatest "swansong" plant was probably "Lilium mackliniae", found jointly with his second wife after whom it is named. At age 68 he climbed to over 1,730–2,590 metres (5,680–8,500 ft) above sea level in the Ukhrul district of Manipur, India (near the boundary of Myanmar to the east) and was still discovering new species of plants on his last expedition in 1956, including "Roscoea australis", the most southerly representative of its genus.