To F. J. Cohn   26 July 1877

My dear Sir.

My son Francis has dispatched to you by this days post a copy of his paper on certain filaments (apparently protoplasmic) which are protruded from the leaf glands of Dipsacus sylvestris. This subject interests me greatly & I have thought that you would excuse my drawing your attention to it—¹ We have in England hardly any one who has attended to the Physiology of plants, but several skilled zoologists, have seen the moving filaments & been astonished at them— If you could persuade any of your pupils to examine these glands & report on them in some Journal I should feel extremely grateful— I hope that you yourself will just look at them

It is a great satisfaction to me to remember your short visit to Down,² & I remain | my dear Sir. | Yours very faithfully. | Charles Darwin.

P.S. | To see the filaments it is best to cut thin transverse sections of the young leaves, growing in the axils of the main leaves— It is of importance that the leaves should be perfectly fresh without any drying, therefore put them in water directly gathered. They are seen best mounted in water.