This puzzle is from the Futility Closet website. According to the description:

One other notable problem from Sam Loyd’s Cyclopedia of 5000 Puzzles: A father left to his four sons this square field, with the instruction that they divide it into four pieces, each of the same shape and size, so that each piece of land contained one of the trees. How did they manage it?

Curious about the solution? Just click here.