CHAPTER III 



THE LESSON OF THE BRITISH FLORA 



Results of observations on the buoyancy of over 300 British plants. — The small 

 proportion of plants with buoyant seeds or seedvessels. — Their station by 

 the water-side. — The great sifting experiment of the ages. — Summary. 



The singular relation between station and seecl-buoyancy that 

 exists in an island of the tropical Pacific, such for instance 

 as Vanua Levu, Tahiti, or Hawaii, would lose much of its 

 significance if it stood alone in the economy of plant-life. It 

 must be true not only of tropical floras generally, but of those 

 of the temperate regions ; and there can be little doubt that it 

 prevails all over the world. Displayed to us at first in a Pacific 

 island, it acquires a new significance when we study it in the light 

 of numerous observations made in Europe. It exhibits itself then 

 as part of a far wider method pursued by Nature in determining 

 the stations of plants. It is not only at the coast, but also at the 

 river-bank and at the lake-side that Nature " locates " the plant 

 with the buoyant seed or seedvessel. This relation is indeed 

 as well exhibited in inland districts as it is at the coast. 



In this connection I have the results of my own investigations 

 on the buoyancy of the seeds and fruits of British plants and on 

 the composition of the seed-drift of ponds and rivers, which were 

 carried on in the years 1890 — 96. Some of them were published 

 in a short paper on the seed-drift of the Thames, read before the 

 Linnean Society of London in June, 1892, and in the columns of 

 Science Gossip for April, May, and October, 1895 ; but the mass of 

 the observations remain in my notebooks. Nor do my observa- 

 tions of the period since elapsed lead me to alter the position then 

 adopted. I have since pursued the same line of inquiry in Hawaii, 



