I have made an interesting, and, so far as I know, a new observation on the spontaneous movements of a fern, the Asplenium Trichomanes.² Last October I took up several roots of this fern, together with some other plants, for the purpose of making a little window garden.

I set out the plants in a large glass dish having a cover. After the plants were rooted, and the ferns had begun to push up and unroll new fronds, I noticed that when I set the dish in the sunshine and removed the cover, as I did every morning, one of the old, or original fronds began to move up and down with exactly the motion of a bending and straightening finger. The frond is about two and a quarter inches long and the movement, until quite recently, extended over a space of three fourths of an inch, or through an arc of about twenty five degrees.

The time of passing from one limit of motion to the other was a little less than three seconds. I at first thought that the motion was in a straight line; that the downward path was in the same line as the upward; but more exact observation has convinced me that the end of the frond moves, with the sun, in a long, very narrow ellipse. This frond was fully developed when I took it up late in October last (1879) and at that time was certainly a month old; so that at this time      it is      months³ old and yet retains sufficient sensitiveness or irritability to move promptly, up and down, under the stimulus of light, though it does not move through as large an arc as it did at first. A curious effect of artificial light on it may be worth noting. Placing the dish, with the cover removed, under strong gas light, the fern began to move as promptly as if in sunshine; but after six or eight minutes the motion ceased and was not resumed.

Other fronds of the same species of fern have motions of the same character but much slighter, and an additional fact which had entirely escaped me was noticed at once by the trained eye of D^r. Asa Gray who happened to be in Washington and was sufficiently interested in my fern to visit it, that it is the fertile or spore-bearing fronds only which exhibit motion.⁴

E. J. Loomis | Nautical Almanac Office

Washington D.C.