3 68 THE POPULAR SCIENCE MONTHLY. 



ginella convoluta, one of the Tycopodiacece, and a native of South 

 America, has the same strange habit ; for, when the ground where it 

 grows becomes parched and dried up, it curls itself up in a ball, loosens 

 itself from the earth, and is then whirled along over the ground by the 

 wind. When it reaches a place suitable for its growth it uncurls itself, 

 takes root, and flourishes till its new home dries up, when it betakes 

 itself in the same manner to a new locality. 



The brief but violent hurricanes of the tropics, which sweep over 

 the land, uprooting trees, overturning houses, and leaving death and 

 desolation behind them, would contribute greatly to a wide disper- 

 sion of seeds which would otherwise be but slightly distributed. The 

 tornadoes and cyclones which not infrequently visit the temperate 

 parts of North America would also act a part in this work. An ac- 

 count given by Humboldt shows a possible means of transport over 

 high hills or even mountains. He says "M. Boussingault and Don 

 Mariano de Rivero saw in the middle of the day, about noon, whitish, 

 shining bodies rise from the valley of Caracas, to the summit of the 

 Scilla, five thousand seven hundred and fifty-five feet high, and then 

 sink down toward the neighborinsr seacoast. The movements con- 

 tinued uninterruptedly for the space of an hour, and the objects, which 

 were at first taken for a flock of small birds, proved to be small ag- 

 glomerations of straw or blades of grass. Boussingault sent me some 

 of the straws, which were immediately recognized by Professor Kunth 

 for a species of Vilfa (V. tenacissima), a grass which, together with 

 Agrostis, is very abundant in the provinces of Caracas and Cumana." * 



Let us now turn to another method of transport. As we have seen 

 that, as a general thing, only light seeds, or those with a feathery ap- 

 pendage, are capable of being distributed by the wind, so we shall find 

 that the ones dispersed by means of ocean-currents are of an entirely 

 different character. This must necessarily be the case ; for those capa- 

 ble of resisting the action of sea-water for a long time must be inclosed 

 in hard shells. The Gulf Stream, that river of the ocean, is of great 

 use in this work. By its means, seeds of Entada scandens, and other 

 plants of the West Indies and tropical America, are annually thrown 

 upon the shores of Ireland, Scotland, Norway, and even as far north as 

 Spitzbergen. That many of these seeds would be capable of germi- 

 nating, and of continuing to thrive if the climate were suitable, there 

 can be no doubt. A plant of Guilandina bonduc, one of the Legumi- 

 ?iosce, was raised from a seed cast on the west coast of Ireland. Logs 

 of wood and bodies of Indians, which had been conveyed by ocean- 

 currents from the West Indies, have been cast on the shores of the 

 Azores and Madeira Islands. A Sapindus saponaria, the common 

 soap-berry tree of the West Indies, was raised from a seed found on the 

 south shore of one of the Bermuda Islands.f The fact already noticed, 

 of some of the plants on the coast of Brazil and British Guiana being 

 * "Aspects of Nature," p. 247. + Jones, "Naturalist iu the Bermudas," p. 190. 



