I recently read this quotation in the August 2008 prayer letter of Tom and Jean Zartman, veteran missionaries to Mexico. The quotation is from a man named Griffith John (1831-1912) who ministered in central China about the same time as Hudson Taylor. It should be encouraging for those who are actively working in the spiritual harvest fields of the world.
"The invisible results are, I verily believe, far greater and far more important than the visible. The growth of our work is similar to that of a plant. The root of a plant takes a longer time to grow than the stem, but maturation takes less time than either. The giant oak is wrapped up in that tiny acorn, but to develop it, the acorn must have time to strike its roots, and the sapling must be exposed to the necessary influences. Summer and winter, spring and autumn, the stormy winds and soft breezes have all had a share in it, and were all necessary to the development of the baby oak into the fair tree you see today. So it is with our work. All great work requires time."