64 Means of Dispersal 



the St Gotthard which occurred on August 30th, 1870, when crystals of 

 salt fell, weighing in some cases 0*76 grammes ; these had been brought 

 by air-currents from North Africa or from the nearest points on the 

 sea-coast, a distance of at least 250 kilometres [156 miles]. 



The stone-rain of February 20th, 1907, at Trelex sur Nyon, which 

 Rollier 1 has described, is a more recent example of the same pheno- 

 menon. White quartzose pebbles as large as peas and hazel-nuts 

 were carried by air-currents from some region rich in siliceous rocks, 

 presumably from the south of France or Spain, that is for a distance 

 of more than 100 km. [62 miles]. 



The best proof of the transport of plant-germs over large 

 distances is afforded by the observations on the colonisation of 

 Krakatau. In this case we have definite proof of long-distance dis- 

 persal: Sebesi, the nearest island with plants, is 18'5 km. [11^ miles] 

 distant, and the nearest points of Java and Sumatra are situated 40*8 

 and 37' 1 km. [25^ and 23 miles] respectively from Krakatau. 



The results of Treub's investigation of the island in the year 1886 

 have already been described (pp. 6, 7). The first colonisation of the 

 volcanic cone, and of the interior generally, was effected by entirely 

 different means from that of the shore-region, and almost exclusively 

 by the introduction of plant-germs by wind-agency. Cells of blue- 

 green Algae, Bacteria, Diatoms, the spores of Liverworts, Mosses, 

 and Ferns, and the seeds of at least six of the eight phanerogams 

 which Treub found in the interior of the island were carried by air- 

 currents. The first phase of colonisation was characterised by the 

 predominance of Ferns, which were represented by 11 species widely 

 distributed in the Indo-Malayan region. Since then there has been 

 a considerable increase in the number of wind-borne species including, 

 in addition to Ferns, members of the Gramineae, Cyperaceae, and 

 Orchidaceae. 



Penzig estimates that the following seventeen species (32 / o of 

 the total flora), recorded from Krakatau up to the year 1897, were 

 introduced by the agency of wind : all the Composites (eight species : 

 Wedelia asperrima, Wedelia scabriuscula, Blv/mea balsamifera, 

 Blumea hieracifolia, Pluchea indica, Vemonia cinerea, Emilia 

 sonchifolia, Wollastonia sp.), five species of Gramineae (GymnotJirix 

 elegans, Phragmites Roxburghii, Imperata arundinacea, Saccha- 

 rum spontancum, Pogonatlievum orinitmn), and the four Orchids 

 (Spathoglottis plicata, Vanda Sulingi, Arundina speciosa and 



1 Rollier, L. "Une pluie de pierres survenue a Trelex (Vaud) le 20 fevrier, 1907." 

 Archives des sciences physiques et naturelles, Oct. et Nov. 1907. (Comptes rendus 

 des travaux presentes a la 90 session de la Societe helcetique des sciences naturelles 

 a Fribourg, 1907, p. 73.) 



