Читать книгу The Circle of Knowledge: A Classified, Simplified, Visualized Book of Answers - Various - Страница 211

In a large number of cases the conveyance of the seeds to a distant point is accomplished by the adoption of the screw-propeller principle. An excellent example of this is to be seen in the fruits of the sycamore. Here the actual seed is large and heavy, but it is attached to a wing-like expansion. When the fruit falls from the tree the wing revolves with great rapidity, very much on the lines of a propeller blade. This has the effect of controlling the rate of fall, so that the whole contrivance is carried to some distance before the seed is actually brought to earth.