Some of our common British fruits are most perfectly planned to stick or entangle themselves in the wool of sheep or in people's clothes. These, such as the Goosegrass (Robin-run-the-Hedge), Burdock, Forget-me-not, Sanicle, Avens, etc., have very often been described. It is only necessary to examine one's clothes after a walk through rough, broken ground to discover some of them, and the ingenuity and neatness of their tiny hooks, harpoons, or prongs can then be realized. We shall give one or two instances of some other spiny plants. There is, for instance, Xanthium, which is one of the Daisy flowers or Composites. Unlike most of this order, its little fruits possess no wind-hairs. The outside of the head of flowers is covered by strong curved little crooks. These get so entangled in wool or hair that they become a perfect pest to wool merchants. In 1814 Xanthium was unknown in the Crimea, but by 1856 it had covered the whole of the peninsula. In 1828 the Russian cavalry horses brought it on their manes and tails into Wallachia, from whence it travelled to Servia. Servian pigs carried it into Hungary. In 1830 it was taken in wool to Vienna. By 1871 it had reached Paris and Edinburgh. In 1860 Frauenfeld saw horses in Chile whose manes and tails were so felted together with thousands of these fruits that the animals could scarcely walk. In Australia, where it first appeared in 1850, it has caused a very serious loss to the wool merchants and squatters. The loss has been put at 50 per cent. by some authorities.[116]
We have already alluded to the transference of fruits and seeds by ocean currents. In the Challenger expedition, no less than ninety-seven kinds of marine floating fruits were observed.
Amongst these the most important is the Cocoanut. The nut sold in this country is not the whole fruit, but only the inside shell. In the natural state this is enclosed in a dense mass of fibres, which form the valuable "coir" used for brushmaking and a variety of purposes.
The entire outside of the fruit is covered by a smooth white skin. The whole fruit is about the size of a man's head, and is so light that it floats easily in the water. It has in fact been carried by the waves to uninhabited islands all over the South Seas. It is a very great blessing to Polynesia, for a tree yields thirty to fifty nuts, and four of these nuts will furnish enough food for one day. Coprah and the oil extracted by boiling the inside are also valuable. Spirit or toddy can be made from the young buds. The leaves are used for thatching and the trunk for timber.
There are other very curious palm fruits which are also carried by water. Sir Joseph Hooker mentions the large, round fruits of Nipa, as big as a cannon-ball, turned over by the paddles of the steamer in the muddy waters at the Ganges mouth (Himalayan Journal).
In this country a search in the rubbish left by a spate or freshet along a riverside is sure to furnish many floating fruits or seeds. Most of these are small and rather difficult to see. Perhaps the most interesting are those of the Sedges. The real fruit is only about one-sixteenth of an inch in size, but it is enclosed in a little sack or bag a quarter of an inch long and with a narrow opening, so that it floats quite easily. Many willow branches, pondweeds, hornweeds, and the like, are also found in the rubbish left by floods, and these can often take root.
It is, however, in the exquisite modifications of those fruits which are blown by the wind that we find the most beautiful contrivances of all. They are effective also. Seeds are often so small as to be like dust particles, and such may be carried in the air to almost incredible distances. That of Goodyera repens weighs only 1/200,000,000 of a pound, that of Monotropa, ·000,000,006 lb. It is no doubt by the wind that the spores of lichens are carried from one mountain to another. On a map of the world the distance from the Arctic to the Antarctic, between the North and South Poles, seems enormous. Moreover, the amount of water, desert, tropical forest, and cultivated land in this extent of country is very great. There are but few rocks on which lichens could manage to grow. And yet of the Antarctic Lichens in the South Polar regions, and which are also European species, more than 73 per cent. are found in the Arctic or North Polar regions.[117]
An Arctic lichen spore probably travelled from Scandinavia to the German and Swiss Alps, another journey took it to the Atlas Mountains, thence to Abyssinia, again to Mount Kenia, and from there, somehow, it wandered to the South Orkneys or King Edward VII Land.
While talking of lichens, one must not forget the Manna of the Bible (Lecanora esculenta) and two other species, which form warted, wrinkled masses on rocks. It breaks off and may be carried away by the wind, or in heavy rain it may be washed into depressions of the soil, where a man can pick up 8 to 12 lb. in a day.
It "is used as a substitute for corn in years of famine—being ground in the same way and baked into bread.... It is also remarkable that all the great so-called rains of manna, of which news has come from the East to Europe, especially those of the years 1824, 1828, 1841, 1846, 1863, and 1864, occurred at the beginning of the year, between January and March, i.e. at the time of the heaviest rains.... The inhabitants of the district actually thought that the manna had fallen from heaven, and quite overlooked the fact that this vegetable structure grew and developed (although only in isolated patches and principally as crusts on stones) in the immediate neighbourhood of the spots where they collected it."[118]