Dr Rayner replied:
I regret that I am unable to assit you very much with the query in your letter of 23 July. I am not aware of any biblical reason for the association of arum lilies with funerals.
One possibility is that in other countries they are extremely expensive (I am told that in Japan and England they can cost up to $100 each) and so are kept for special and important occasions such as weddings and funerals. It may be that the superstition has built up around this fact. This is, however, speculation and there is certainly no biblical basis so far as I am aware.