THE DISPERSION OK SEEDS AND SPOKES. 67 



resist its influence is proved by the fact that on the 

 coasts of Norway various Mexican seeds and fruits 

 are washed ashore from the Gulf Stream, still 

 retaining their germinating power. " Crabs'-eyes," 

 or the black-and-red paternoster-seeds of Abrus 

 precatorius, are washed up on the shores of many 

 tropical countries, and the tree is common along 

 their coasts. It is difficult to resist the conviction 

 that this is also the end served by the thick woody 

 envelope of the cocoa-nut, for in this way its wide 

 range could be easily accounted for. Such a thick 

 woody pericarp would be of the greatest service in 

 the case of a seed transported by ocean currents 

 and washed ashore through a heavy surf upon a 

 newly emerged coral - reef. The need for such 

 protection is of course great where, as is the case 

 in the cocoa-nut, the seed is so large and its contents 

 so perishable in their nature. One is inclined to 

 view the shell of the hazel-nut in the same light. 

 When one remembers that hazels commonly grow 

 on the banks of streams, it seems not improbable 

 that the hard shell or pericarp is an adaptation 

 favouring its distribution by means of floods. This 

 explanation, however, it must be admitted, does not 

 apply very well to the shell of the acorn. Many 

 alpine plants have their seeds carried down, as we 

 know, by mountain streams, and cast up on their 

 banks at lower levels. Everyone must have noticed 

 in climbing any of our higher mountains how alpine 

 species of Saxifraga, Galium, Alchemilla, etc., are thus 

 brought down far below their natural levels. 



The flat smooth fruit of the arrow-head {Sagittaria 

 sagittifolia) has an oily rind not easily wetted. This 

 fruit appears adapted for transport either by wind 

 or by water. And this may possibly be an advantage 

 to a plant which, like Sagittaria, grows in shallow 

 waters which, at the time when its fruit is ripe, are 

 very likely to dry up more or less completely. 



Icebergs drifting from polar seas are often freighted 

 with quantities of stones and earth. Seeds and 



