Mendel's laws (like the laws of segregation or inheritance) became known to a wider publis decades after he discovered these laws. He assumed trait particles in operation that were responible for his observed laws.
Darwin is known for his rheory of evolution. DNA was not known to him. He considered organisms as a whole that evolved. Later his views were reduced to the level of genes (Dawkins). The genes are seen as the (selfish) units around which evolution takes place. All evolution is directed towards the prolongation of the genes and organisms are seen as a means to an end. We have sex to pass through our genes. This is a far cry from the organism centered view in which the genes perform a secondary (altruistic) role. We have sex to make a new organism live. Obviously this also results in the passing through of genes but the meaning of (objective) evolution is drastically changed. When questioning this paradigm of the selfish gene the reaction many molecular biologists is an irrational one. Their view can't be questioned. I asked three questions about this on the biology site and they were all downvoted massively and I couldn't comment anymore. My last question didn't even make it and I was suspended within an hour. Which only goes to show how rigid and conservative and irrational they are.
But that aside. What were the basis entities of Mendel and Darwin in the context of evolution. They certainly knew each other. But they never met. Was Mendel even in favour of evolution?