Doubt about aov and lm function... bug?

There is no bug.

Both of your examples work fine for me.  

Ditto

You may have a corrupt

version of ``iris'' somewhere in your search path before ``datasets''.

What does find("iris") tell you?  What does names("iris") tell you?

Could also be something interfering with the model.frame/model.matrix 
bits. The error message suggests that something did a substitute of ".", 
but I can't offhand see a parse(text=x) construct in any of the usual 
suspects. A traceback() could be informative.

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