In an earlier article "Pitcher-plants of East Malaysia and Brunei"
(Nature
Malaysiana, Vol 13, No 4, Oct 1988), Phillipps & Lamb showed a
photograph on page 9 entitled "The natural hybrid N. x trichocarpa
(sic): N. rafflesiana crossed with N. gracilis". This natural hybrid
(N. rafflesiana x N. gracilis) is included in the text giving the list
of names of hybrids "so far recorded in the wild", on the same page.
Incidentally, I have seen the natural hybrid in several locations
within a 150
kilometres of Singapore, where I live. Regards and Happy CP'ing,
Wee
Kiat.