Amongst the wind-blown fruits and seeds there are cases in which entire plants are dragged out of the soil and hurried away by the wind, which rolls them over and over. They may be blown along for days together. The seeds drop out by the way. In this country one rarely sees anything of the sort, but in the Prairies of North America, when under cultivation, these tumble-weeds are a serious and expensive pest. Sometimes the farmers dig trenches to catch them, or they may put up fences against which the tumble-weeds become piled or heaped up until they blow over the top. It is not very much use to give the names of these weeds, for they are mostly rare or not British species. Such tumble-weeds are generally nearly spherical in general form and have a short, rather weak, root which is easily torn out of the ground. In some grasses, such as "Old Witch," a well-known pest of the United States, the grass-stalk, with many flowers on it, is pulled out of its sheath and blown away. But it is more usual for the fruits or seeds themselves to break off the parent plant, and to be carried away by the wind. To this end we find the most extraordinary changes. Although the flower may droop from its stalk, the latter becomes upright and grows quite a considerable length when the seed or fruit is dispatched on its wanderings. This will raise the fruit or seed as high as possible above the surrounding grasses. Then in some cases the fruit opens to allow the seed to escape. Small holes appear in it, or the fruit splits. As the dry, elastic, withered stalk swings to and fro in the wind, the seeds are swung out of these openings, and starting with a certain momentum the wind will carry them often to a surprising distance from their parents. In wet or rainy weather these holes or slits generally close together, and no seeds are sent forth on their travels. The little holes in the top of a poppy-head by which the seeds are swung out have little flaps, which close over and shut them up in wet weather.