E. V. Wulff — 118— Historical Plant Geography 



impossible, in consequence whereof they are doomed to perish, but 

 sometimes, due to a sudden change in conditions, seeds accumulated 

 perhaps over a period of years and lying dormant suddenly find it 

 possible to develop. This may occur, for example, when a forest is cut 

 down, when there may be observed the unexpected development of a 

 number of species that formerly could not grow in this forest but 

 whose seeds were borne each year into the forest and to a partial ex- 

 tent remained inviolate and preserved their ability to germinate. In 

 mountainous regions the wind carries seeds over hills and mountain 

 passes, wafting them to considerable heights, whence they fall, how- 

 ever, at not a great distance from the mother plants. Thus, according 

 to HxJMBOLDT, BoussiNGAULT saw sccds lifted by the wind to a height 

 of 5,400 m., whence they again fell not far from their original loca- 

 tion. 



But, notwithstanding such irrefutable facts, de Candolle doubts that 

 seeds are borne by the wind over great distances. He never heard, for 

 instance, of seeds being carried by winds from England to France or 

 from Ireland to England; he never had proof of the transport by wind 

 of seeds from Africa to Sardinia, from Sardinia to Corsica, or from 

 Corsica to the shores of the mainland near Genoa or Nice, despite the 

 force of the south winds prevailing there. He bases his conclusions 

 also on other authorities on the problem of the dispersal of plants, such 

 as GussoNE, GoDRON, and Lyell, and also on the testimony of sailors, 

 who observed the transport by wind of winged insects or dust to the 

 decks of ships but never saw seeds. Hurricanes, such as rage, for 

 example, over the Antilles or along the Chinese coast, must, of course, 

 also carry with them numerous seeds and even fruits, but these hurri- 

 canes are, for the most part, purely local in character and revolve in a 

 circle whose diameter is not very large. An important point made by 

 DE Candolle is that wind can be of great significance in seed dis- 

 persal only in case of their mass accumulation, which never occurs. 



Kerner (1871; 1 891) noted that on sunny, windless days numerous 

 plumed seeds and fruits are borne aloft to a considerable height by 

 ascending air currents. He tried to determine the number of such 

 seeds and counted during one minute as many as 280 seeds floating past 

 him and rising in a current of air, so that it may be presumed that the 

 total number of such seeds borne upward by atmospheric currents 

 during a single day amounts to several millions. Nevertheless, for the 

 dispersal of plants over great distances this has no significance, since 

 after sunset these seeds and fruits again alight not far from the place 

 whence they were lifted. Kerner further points out that in some 

 plants the special adaptations for flight remain attached to the fruits 

 or seeds only during the first flight; once the latter have alighted, 

 these adaptations fall off. This is true particularly in the case of 

 pine seeds, which after they have once alighted are no longer able 

 to fly; it also holds true in the case of many Compositae, whose 

 plumed achenes, drifting with the wind, at the slightest collision 

 with some obstacle become detached from their plumes and fall to the 

 ground. 



Ridley (1930, pp. 131-2) points out that, in the case of plumed 

 fruits, in measuring the distance to which they may be carried by the 



