CHAP, xir THE AZORES 257 



object in the present work is to trace the past history of 

 the more important islands by means of the forms of life 

 that inhabit them, and as for this purpose plants are some- 

 times of more vakie than any class of animals, it will be 

 well to take advantage of the valuable materials here avail- 

 able, in order to ascertain how far the evidence derived 

 from the two organic kingdoms agrees in character ; and 

 also to obtain some general results which may be of service 

 in our discussion of more difficult and more complex 

 problems. 



There are in the Azores 480 known species of flowering- 

 plants and ferns, of which no less than 442 are found also 

 in Europe, Madeira, or the Canary Islands ; while thirty- 

 eight are peculictr to the Azores, but are more or less closely 

 allied to European species. As botanists are no less prone 

 than zoologists to invoke former land-connections and 

 continental extensions to account for the wide dispersal of 

 objects of their study, it will be well to examine somewhat 

 closely what these fa.cts really imply. 



The Dispersal of Seeds. — The seeds of plants are liable 

 to be dispersed by a greater variety of agents than any 

 other organisms, while their tenacity of life, under varying 

 conditions of heat and cold, drought and moisture, is ex- 

 ceptionally great. They have also an advantage, in that 

 the great majority of flowering plants have the sexes united 

 in the same individual, so that a single seed in a state fit 

 to germinate may easily stock a whole island. The dis- 

 persal of seeds has been studied by Sir Joseph Hooker, 

 Mr. Darwin, and many other writers, who have made it 

 sufficiently clear that they are in many cases liable to be 

 carried enormous distances. An immense number are 

 specially adapted to be carried by the wind, through the 

 possession of down or hairs, or membranous wings or pro- 

 cesses ; while others are so minute, and produced in such 

 profusion, that it is difficult to place a limit to the distance 

 they might be carried by gales of wind or hurricanes. 

 Another class of somewhat heavier seeds or dry fruits are 

 capable of being exposed for a long time to sea- water with- 

 out injury. Mr. Darwin made many experiments on this 

 point, and he found that many seeds, especially of Atriplex, 



S 



