CHAPTER IV 



THE LESSON OF THE BRITISH FLORA {c07ltinued) 



The choice of station of the water-side plant possessing buoyant seeds or seed- 

 vessels.— Determined by its fitness or unfitness for living in physiologically 

 dry stations. — In the internal organisation of a plant lies the first de- 

 termining influence of station. — The grouping of the British strand-plants. — 

 Whilst the Xerophyte with buoyant seed or fruit finds its station at the 

 coast, the Hygrophyte similarly endowed makes its home at the river or 

 pond side. — The grouping of the plants of the river and the pond. — 

 Summary. 



By following up the clue supplied by the floating seed, we have 

 arrived at the conclusion with respect to the British flora that 

 plants with buoyant seeds or fruits gather at the water-side. But 

 we have yet to inquire why some of these plants are " located " at 

 the sea-coast and others on the borders of ponds and rivers. Mere 

 buoyancy aided by chance has not determined the choice. There 

 are definite principles at work in the economy of plant-life that 

 make the selection for each plant. 



Rivers in all parts of the world carry to the sea in great 

 abundance the seeds and fruits of the plants that are stationed 

 at their borders ; and such seed-drift is found in quantity washed 

 up on the beaches in the vicinity of the estuary. One finds, for 

 instance, on such beaches in the South of England the stranded 

 fruits and seeds of Bidens cernua, Alnus glutinosa, Sparganium 

 ramosum, Iris pseudacorus, &c., mingled with those of true beach 

 plants like Cakile maritima, Convolvulus soldanella, Euphorbia 

 paralias, &c. Yet we would be much surprised if either the Bidens 

 or the Alder or the Sparganium were to establish itself on the 

 sandy beach, even though they have had through the ages in- 

 numerable opportunities of doing so. We thus see that mere 



