THE AZORES 



439 



4. In the case of the aquatic and subaquatic plants it is shown that 

 whilst those with small seeds, such as Peplis, Littorella, etc., would 

 be dispersed by waterfowl that would be likely to carry dried mud 

 on their feet and legs, others like Potamogeton, Car ex, Scirpus, etc., 

 possess small fruits that are known to be swallowed and ejected 

 unharmed by waterfowl (p. 420). 



5. As in temperate latitudes, currents have not taken a prominent 

 part in stocking the seashore plants of the Azores with their plants,., 

 unless we include the intermediate agency of the drifting log; and: 

 appeal is made to a variety of other dispersing agents (p. 420). 



6. In regard to the strenuous appeal of Wallace for the paramount 

 influence of winds over birds in transporting small seeds like those 

 of Sagina and Orchis over tracts of ocean 1000 miles in width, it is 

 remarked that although there seems to be no question about the 

 fitness of the spores of cryptogams for dispersion by winds across 

 the ocean it is concerning the seeds of flowering plants that doubts 

 would be raised. In this connection the results of the experiments 

 of Lloyd Praeger on the falling rates of seeds are utilised to show that 

 the great contrast in weight between the smallest seeds of flowering 

 plants and the spores of cryptogams reflects the difference between 

 inefficient and efficient dispersal by winds over great distances. 

 Though so minute in size and so light in weight, the seed of an orchid 

 falls through the air at least fifty times as fast as an ordinary mush- 

 room spore. To counteract the effects of gravity, as measured by 

 the falling rates of seeds and spores, an initial elevation at the starting- 

 place must be assumed ; and it is shown that before a wind blowing 

 at the speed of fifty miles an hour, the initial altitude requisite for 

 a spore or seed to reach the Azores from the European sea-borders ; 

 would be only a few hundred feet for a mushroom spore and nearly' 

 ten miles for an orchid seed. It is shown, however, that witfcu 

 " plumed seeds," such as those of Typha and Epilobium, the difficulty 

 is not quite so great; but even here an initial elevation of 20,000 

 feet would be required in the first case and of 35,000 feet in the second 

 case to reach the Azores. It is urged that the up- draught on the 

 slopes of lofty mountains would provide the initial altitude for 

 cryptogamic spores and perhaps also for plumed seeds of the types 

 above named. But this would be impossible both for the seeds of 

 orchids and for the pappus-fruits of Composite plants, like Senecio 

 and Sonchus, where initial elevations of nine or ten miles would be 

 needed (p. 422). 



7. The last part of the chapter is devoted to notes on the plants 

 of the Azores (p. 425). 



LIST OF WORKS DEALING WITH THE PLANTS OF THE AZORES OR 

 QUOTED IN THE DISCUSSION IN THIS AND THE TWO PRECEDING 

 CHAPTERS 



(See also list of works on Azorean botany in Trelease's paper below mentioned.) 



Ball, J.,. The Mountain Flora of the Great Atlas, given in Hooker's book on Marocco 



below named. 

 Beirao, C. M. F. da S. See under Gomes. 

 Boid, Description of the Azores : London, 1835. 



