Many of the plants he has collected are disappearing quickly. When he goes out to check whether specific species still grow where records show them to have been found in the past, six or seven times out of ten he finds that conditions at the locations described in the literature have changed and the plants are gone.
許多水生植物之所以需要他山窮水複的尋覓，正因為它們消失的太快，他根據過去的紀錄踏勘，十回總有六、七回發現原來的環境早已改觀，植物已不見蹤影。