150 HEREDITY AND EVOLUTION IN PLANTS 



seeds were dispersed on floating logs; and the small seeds 

 of several species were safely transported in the crevices 

 and holes made in small stems and branches by worms and 

 molluscs. Other seeds were floated on blocks of pumice. 



In Hawaii, while nearly 85 per cent, of the spermato- 

 phyte flora is endemic (see p. 165), about 70 per cent, 

 of the species of the coastal zone are introduced. This 

 is in marked contrast to the general rule for oceanic 

 islands, whose littoral floras, as might be expected, are 

 predominantly cosmopolitan. In this particular case 

 MacCaughey attributes very great importance to ocean 

 currents as agents of dispersal. The natives of these 

 islands, at the time of their discovery, are reported to have 

 had large canoes hewn from tree trunks of the Douglas 

 spruce, which could have come only from the north- 

 west shores of North America; and considerable numbers 

 of tree trunks and large branches are brought from the 

 same coasts to Hawaii each year. Ocean currents also 

 bring annually large quantities of plant material to the 

 coast of other oceanic islands. Tansly and Fritsch have 

 noted large numbers of young seedlings and germinating 

 seeds in drift material on the coast of Ceylon, and Moseley 

 observed many living plants in the coastal drift of the 

 Moluccas, including trees, palms, epiphytic orchids, and 

 large quantities of fruits containing viable seeds. 



Seeds are carried by birds in mud adhering to their 

 feet, lodged in their feathers, and in the alimentary canal. 

 In mud adhering to the feet of a partridge Darwin found 

 82 seeds that germinated. Wallace is authority for the 

 statement that "all the trees and shrubs in the Azores 

 bear berries or small fruits which are eaten by birds; 

 while all those which bear larger fruits, or are eaten 



