Seed-dispersal 

 Selection 



SCIENTIFIC SIDE-LIGHTS 



614 



Against the dark green of the leaves, the 

 berries stand out with great prominence. 

 Their after-history is instructive enough. A 

 holly-berry is gobbled up by a bird with 

 ease. What of the seeds the berries contain ? 

 Does digestion, which in a bird is a tolerably 

 rough and mechanical process, destroy the 

 seeds? Not so. The seeds, encased each in 

 its dense tough covering, resist even the di- 

 gestion of the bird's gizzard and stomach, 

 and they are passed on uninjured through 

 the alimentary tract of the animal. Thus 

 liberated, and the bird being the gainer by 

 its digestion of the soft parts of the berries, 

 the holly-seeds fall into the soil and grow 

 up each in time to the holly-tree. Note 

 again how this interaction between bird and 

 fruit serves another useful purpose. Birds 

 traverse leagues of country in their peregri- 

 nations. They may thus convey the holly- 

 seeds to regions hundreds of miles from the 

 parent tree whence the berries were plucked. 

 . . . We owe much to the dispersal of 

 seeds by such agencies. There is a plant of 

 the New World, the American currant, 

 which long ago was introduced into France, 

 for the sake of the dark red juice of its 

 berries, which was used to color wines. 

 At Bordeaux this currant was extensively 

 cultivated. Man introduced the plant, but 

 mark the greater influence of the color of its 

 fruits and the work of the birds. Now, the 

 American currant is found universally 

 throughout the south of France. It has 

 spread also into Switzerland, and has 

 reached the Tyrol. You can, therefore, 

 prophesy with considerable safety regarding 

 plants and their chances of distribution, 

 when you see these fruits and learn the 

 story of their distribution. Holly-berries 

 have social associations dear to the hearts 

 of us all. They possess, however, in their 

 redness and in their attraction for bird-visit- 

 ors, a romance that is all their own. WIL- 

 SON Glimpses of Nature, ch. 22, p. 73. 

 (Hum., 1892.) 



3036. 



Seeds Flung Afar 



The " Catapult Fruits." The calyx of 

 sage, bergamot, and most other mints re- 

 mains dry and stiff, as a cup to hold one to 

 four little round nutlets as they ripen. 

 . . . When dry, the plant behaves some- 

 what as follows: when the wind jostles the 

 branches against each other, or when an 

 animal of some kind hits the plant, this 

 movement causes many of these cups to get 

 caught ; but the elastic stem comes suddenly 

 back to its place, and in so doing flips a nut- 

 let or more from its mouth one to six feet, 

 somewhat as a boy would flip a pea with a 

 pea-shooter. In our garden, July 2, when 

 plants of sage, Salvia interrupta, were 

 ripening their fruit, we found it difficult to 

 collect any seeds, but seedlings were ob- 

 served in abundance on every side of the 

 plant, some to the distance of six feet. 

 Plants dispersing seeds in this manner have 



been called catapult fruits. BEAL Seed Dis- 

 persal, ch. 5, p. 50. (G. & Co., 1898.) 



3O37. Seeds Scattered 



Like Snowftakes. The seeds of willow and 

 poplar are covered with white downy silk, 

 by means of which they are borne through 

 the air in summer, often so filling it as to 

 suggest a light snow-storm. WEED Seed 

 Travellers, ch. 1, p. 3. (G. & Co., 1899.) 



3038. 



Seeds Transported 



by Rivers. " The mountain stream or tor- 

 rent," observes Keith, " washes down to the 

 valley the seeds which may accidentally fall 

 into it, or which it may happen to sweep from 

 its banks when it suddenly overflows them. 

 The broad and majestic river, winding along 

 the extensive plain, and traversing the con- 

 tinents of the world, conveys to the distance 

 of many hundreds of miles the seeds that 

 may have vegetated at its source. Thus the 

 southern shores of the Baltic are visited by 

 seeds which grew in the interior of Ger- 

 many, and the western shores of the Atlan- 

 tic by seeds that have been generated in the 

 interior of America." Fruits, moreover, in- 

 digenous to America and the West Indies, 

 such as that of the Mimosa scandens, the 

 cashewnut and others, have been known to 

 be drifted across the Atlantic by the Gulf 

 Stream, on the western coasts of Europe, in 

 such a state that they might have vegetated 

 had the climate and soil been favorable. 

 Among these the Guilandina Bonduc, a legu- 

 minous plant, is particularly mentioned, as 

 having been raised from a seed found on the 

 west coast of Ireland. LYELL Principles of 

 Geology, bk. iii, ch. 37, p. 620. (A., 1854.) 



3039. 



Seeds Transported 



in Mud Animals as Seed Distributors. 

 Seeds and fruits of aquatic and bog plants 

 that are floating, or in the mud of shallow 

 water, are often carried by ducks, herons, 

 swallows, muskrats, and other frequenters 

 of such places, on their feet, beaks, or feath- 

 ers, as they hastily leave one place for an- 

 other. In this way seeds of water plantain, 

 sedges, grasses, rushes, docks, arrowhead, 

 pondweeds, duckweed, cat-tail flag, bur reed, 

 bladderwort, water crowfoot, and many oth- 

 ers are transported from one pond, lake, or 

 stream to another. In some cases enough 

 of a living plant may be detached and car- 

 ried away to keep on growing. Darwin 

 found on the feet of some birds six and 

 three-quarter ounces of mud, in which were 

 five hundred and thirty-seven seeds that 

 germinated. Mud may be carried on the 

 feet of land animals as well as on aquatic 

 animals, not only from the ponds and bogs, 

 but from the fields where seeds may have 

 accumulated in the earth or washed down 

 the slopes. BEAL Seed Dispersal, ch. 7, p. 

 71. (G. & Co., 1898.) 



3O4O. 



Worms Bury Seeds 



in the Earth Chambers under Ground Care- 

 fulljl Lined by Worm Builders. I found at 

 Abinger, in Surrey, two burrows termina- 



