Nobody knows what starts the sap running along the twigs of a very young, tender and springlike woman's nature. In Betty's case, it is Samuel Foster Crittenden -- even though she hardly realizes it. She leaves America for a traipse across Europe, to take in the sights, and sends him a postcard now and then . . .And then when she returns home, she finds him in dirty overalls -- for Sam has become a farmer!"You can seal friends up in your heart and forget about them -- and when you take them out they are perfectly fresh and good," Betty says to herself. "But they may have changed flavor!"