Many years ago I read a horror story as part of a collection (maybe one of the Pan Book of Horror series). All I remember is that there were two men, possibly on a small boat, making their way through some jungle. Some kind of horrible supernatural plant caused them to become catatonic and as they looked on it wound its white tendrils around them and pushed them into their eyes and there was nothing they could do about it. Can't find it - any ideas welcome!

I've managed to find it (by chance). The story is 'The Seed from the Sepulchre' by
Clark Ashton Smith and it can be read here should anyone be interested:

The Seed from the Sepulchre by Clark Ashton Smith (http://www.eldritchdark.com/writings/short-stories/191/the-seed-from-the-sepulchre)

If anyone had looked for this thank you!