The advocatus diaboli has a useful function in science. But in attacking Darwin his brief is generally found to be founded on a slender basis of facts. Thus Winge and Knud Andersen have examined many thousands of migratory birds and found "that their crops and stomachs were always empty. They never observed any seeds adhering to the feathers, beaks or feet of the birds." (R.F. Scharff, "European Animals", page 64, London, 1907.) The most considerable investigation of the problem of Plant Disp...