30 A NATURALIST IN THE PACIFIC ch. hi 



(c) In the great sorting-process that has been in operation 

 through the ages, nearly all the plants with buoyant seeds or seed- 

 vessels have been located at the water-side, principally by ponds 

 and rivers, but also on the sea-beach. On the other hand, the 

 great majority of the plants with seeds or seed vessels that sink 

 have found a home in drier stations. 



(d) The character of the operation is well displayed in certain 

 genera possessing species of the water-side and species of drier 

 situations, and in the case of genera having both coast and inland 

 species. In both instances the species by the water-side possesses 

 buoyant seeds or fruits, whilst that of the station in a drier locality 

 or removed from the coast has seeds or fruits that sink. 



(e) Yet it is necessary to remember that the principle involved 

 is not that all water-side plants have buoyant seeds or fruits, but 

 merely that plants thus endowed gather at the water-side. There 

 are many plants with non-buoyant seeds or fruits on our beaches 

 and beside our ponds and rivers. 



(/) We have now learned from the British flora that the 

 " locating " of plants with buoyant fruits or seeds on the beaches 

 of the tropical islands of the Pacific, and indeed of tropical regions 

 generally, is but a part of a much wider principle by which plants 

 thus endowed are placed at the water-side, whether by a river or a 

 pond or by the sea. 



(g) It is with this distinction between a fresh-water and a salt- 

 water station that we shall be occupied in the next chapter ; and 

 it is of great interest, since it leads us to discover that the wider 

 principle is in its turn part of a far larger scheme. 



Note. — It must be clearly understood that by water-side plants 

 the true aquatic plants, such as the Water-lilies, the Myriophylls, 

 the Potamogetons, &c., are not implied. It will be seen from the 

 list in Note lo that in most cases the seeds or fruits of aquatic 

 plants have little or no floating power. This is true, for instance, 

 of Ranunculus aquatilis, Nymphasa, Nuphar, Myriophyllum, Cerato- 

 phyllum, Callitriche, Naias, ZannichelHa, Ruppia, and half the 

 Potamogetons. 



