New to gardening I was digging over a patch of garden to put spuds in. I discovered what I thought was an old bit of rubbery, orange, plastic tube, about 1.5cm in diameter. As I "followed" it I realised that it was an old root as there aren't any plants near it. The root split length-ways easilly and was white with orange stripes. My spade cut through it easilly. Any ideas? (Is it something nasty???)