Question
Hi Tom

i was just wondering if it was possible to cross-pollinate a Rose and A daisy. My lifelong friend said it was possible.

Answer
Hi Andrew,
Thanx for your question.  I'm not an expert in botany and that's really what this question is about.  But, I think I can try to answer it for you.  Usually, cross pollination between different genera is usually not possible.  That's why a dog and an ape can't breed.  There is an incompatibility due to a term call gene speciation as I understand it.  When an attempt is made for cross fertilization between two different genera either the sperm is unable to penetrate the egg due to certain chemical inhibitors or if the sperm does unite with the egg the nucleus and mitochondria fail to function.  Like I said, I am by no means an expert in botany and I'm really not comfortable trying to explain this to you even though in my mind, I can understand the mechanics.  One of the reasons I read that Nature has developed speciation is so that organisms will function effectively.  Can you imagine what it would be like if a dog and a fish could breed?  Well, do you think the fish/dog would survive long out of water or in the water?  Which part would die first, the dog part or the fish part?  So, no, a rose and daisy cannot cross pollinate.  Their genera are too dissimilar.  Some genera (such as in the family of orchids) are able to cross pollinate because they share a number of genetic similarities.  Now, plants can be genetically modified and maybe this is what your friend is thinking.  You can take the genes out of one organism and transplant them into another and a viable result will occur.  I hope this helps.
Tom