APPENDIX 



535 



NOTE lo (page 24) 

 The Buoyancy Experiments on British Plants 



The experiments in all cases were made to test the floating power of 

 the seed or fruit in the condition in which it is detached from the plant. 

 It usually makes very little difference whether sea-water or fresh water is 

 employed, since in my numerous experiments there were but few excep- 

 tions to the general rule that seeds or seed-vessels that sink in fresh water 

 sink also in sea-water. This subject is discussed in Chapter X. How- 

 ever, it may be here observed that the chief effect of the increased density 

 of sea-water is merely to increase the proportion of buoyant seeds or fruits 

 in any particular species. 



It is necessary in such experiments to imitate Nature as much as 

 possible. The seed or fruit, as the case may be, must be experimented 

 upon in the condition in which it falls from the plant, or in the condition 

 in which it would be ultimately found in river and pond drift. The seed 

 or fruit should be thoroughly wetted, and air-bubbles removed. 



Prolonged drying has but a slight effect on the great majority of seeds 

 and seed-vessels experimented on, and this is just as true of tropical 

 plants. Those that sink at once in the mature and fresh condition rarely 

 float more than a day or two even after drying for a year. The usual effect 

 is to increase the floating capacity of seeds and fruits already buoyant, and 

 not to develop the capacity. 



The results given in the table refer only to sound seeds. In fresh- 

 water experiments, in nearly all cases, the seeds ultimately germinate in the 

 water, and this is the usual cause of the close of the experiment. In an 

 ordinary collection of floating seed drift from a pond or river, germination 

 will go on for years at each successive spring, the postponement of 

 germination being a very striking feature with a fair proportion of seeds in 

 river and pond-drift. This subject is dealt with in detail in my paper 

 published in the Proceedings for 1897 of the Royal Physical Society of 

 Edinburgh. 



The Table of Results of Observations and Experiments on the 

 Buoyancy of the Seeds or Seed-vessels of more than 300 

 British Flowering Plants 



Explanation of Table. — The capacity of floating for months is thus indicated, -H-H ; of floating 

 for I to 4 weeks, -t- ; and where sinking occurs at once or within a week there is no entry. When 

 buoyancy continued in my experiments after 6 and 12 months, it is indicated by Roman numerals (VI 

 and XII). A=an aquatic plant ; M=a beach plant ; R=a river-side or pond-side plant ; var.=variable 

 in floating power. 



