What's this growth on this tree?

[Faramir]

Hi there,

 

I've always wondered what this lump on the side of what I think is a Plane tree is. What does everyone think?

 

Stupid question: Do trees get 'cancer' as we think of it, or is it more bark the better? If this was on an animal I'd worry about it!

 

..do we use capitalised names for trees like I did just now?

 

thanks all

 

 

 

bigger version of this photo: https://dl.dropbox.com/u/17160874/DSC04651.JPG

[Tony Croft aka hamadryad]

some are caused by fungi, others by bacterium, nematodes also a possibility noones done any indepth research as far as i can tell, I know but is unproven they are found on Oaks associated with fistulina hepatica

[Acg128]

its the only male one there thats its big nut sack !!!!

[MATTMOSS]

Is this not a burr - caused by stress?