Other animals than birds carry fruits and seeds, besides those that eat them. Some fruits like the _Martynia_ (Figure 60), are so arranged that no animal with fur can avoid catching some if they come in contact. The prickly fruits of cocklebur resulted in one species of that weed from the steppes of Russia being carried all over southern Europe in a comparatively few years. Tickseeds, _Bidens_, and all the hosts of plants that have prickles, burs, spines or what not attached to their fruits, have, by the possession of such devices, a better chance for dispersal of their fruits than those not so provided. Others, again, have various coatings of mucilage which stick to animals and thus help plants to overcome their chief drawback to dispersal--their anchorage at the place of birth. THE WIND The great trade winds, the violent hurricanes and monsoons of Asia, are all active and constant aids to plant dispersal. The fruits of many plants are provided with various devices to insure buoyancy in the air, such as maple, ash, and most seeds of pines and their relatives, birches, poplars, and willows, all of which may be carried distances of a few hundred feet in ordinary winds. In the buttonball tree, the milkweeds, fireweed, and many other plants there are feathery attachments or plumes that insure their seeds or fruits being carried very long distances indeed in regular or violent winds. But in the daisy family or _Compositæ_ we find nearly all the eleven thousand species provided with a plumelike attachment of their light fruits, familiar enough in the dandelion, which may explain their being more widely distributed than any other plants. Some of them, however, are carried by animals, as they produce, in certain genera, barbed or hooked achenes. The whole seed of some plants is so small that it can be lifted bodily by the wind, for instance _Rhododendrons_ and many other heaths, one of the hanging pitcher plants of tropical Asia, many orchid seeds, and of hundreds of other plants. Many of these are less than one ten-thousandth of a gram in weight and, with dust and the spores of nearly all cryptogams, may be transported thousands of miles. When it is recalled that the dust from a volcanic eruption at Krakatoa in the Pacific was picked up on London window sills, and that some seeds and nearly all spores are as light as most dust, the wind as a plant dispersal agent becomes significant. In the western part of the United States over 800 million tons of dust are carried over 1,400 inches in a single year, according to estimates by J. W. Evans in his article on “The Wearing Down of Rocks.” Some effects of wind dispersal of seeds and spores furnish interesting data to the plant geographer.