From the California Farmer we learn that a grove of mammoth trees has been discovered in Yosemite valley. The first tree that was measured was eighty feet in circumference three and a half feet from the ground; another tree was ninety feet in circumference at the same distance from the ground, while close to the roots it was one hundred and two feet round it, and it was three hundred feet high. The number of trees measured was one hundred and fifty.five, and they are about half the group; none were less than forty feet in circumference, and there were one hundred over fifty feet. The largest tree now lies upon the ground; it is charred, and .its heavy bark is gone, and yet it measures thirty-three feet in diameter, or one hundred feet in circumference, and must have been four hundred feet high. The Farmer concludes by saying : " This we believe to be the largest tree yet discovered ; and this forest we claim as the Parent Forest of the world."