Male Labrador Retriever not showing interest in breeding

Question
I have a female labrador retriever in heat since possibly last week and a 1 1/2 year old male lab who has never bred before.  He doesn't seem to try to mount her or have any interest in breeding.  He did smell and lick her when I had her lay down, but then just walks away.  Will he show interest later or maybe he doesn't know what to do.  I was told that it will just come natural when she is fertile enough.  Please give me some advise.  Thank-you

Answer
I love dogs and am willing to give hours and hours answering questions from owners that will help the dogs.  I am very concerned about the slaughter of dogs for lack of homes. I am afraid many of the questions here are from poorly informed people breeding dogs.  I can't in good conscience facilitate that.  Go to www.akc.org and read about responsible breeding.  Go to www.petfinder.org and see how many dogs in your area need homes.