538 



A NATURALIST IN THE PACIFIC 



THE TABLE OF RESULTS OF OBSERVATIONS AND EXPERIMENTS ON THE 

 BUOYANCY OF THE SEEDS OR SEED-VESSELS OF MORE THAN 300 

 BRITISH FLOWERING PLANTS (continued} 



Total of the original list : 320 species belonging to 192 genera and 65 families. Of these, about 260 

 were tested by the author, the data for the remaining species being mainly derived from the writings of 

 Thuret, Kolpm-Ravn, and Sernander, with a few from those of Darwin and Martins. 



NOTE. Whilst this work has been going through the press, the author has add^d thirteen species, 

 seven genera, and two families to the list above given ; but the general inferences are not affected by the 

 additions. The corrected total would, therefore, be 333 species, 199 genera, and 67 families. 



On the effect of drying on the buoyancy of seeds and seed-vessels 



It has been already observed that this is as a rule but slight, and that 

 in the great majority of cases the effect of prolonged drying for many 

 months, or even for years, is at the most to give a seed or fruit originally 

 non-buoyant a floating power of a few days' duration. This is a subject to 

 which I have paid especial attention in my experiments, since, of course, 

 much depends on it in the way of dispersal by currents. It is obvious 

 that a seed or fruit possessing impermeable coverings at the time of its 

 separation from the parent can scarcely be compared with one where the 

 coverings only attain their water-proof capacity by drying. Most gardeners 

 know that seeds which dry easily take up moisture easily, and the principle 

 applies in a varying degree to the great majority of seeds and fruits. 



Darwin was inclined to attach importance to adventitious buoyancy 

 acquired by drying ; and in the Origin of Species he refers to instances 

 offered by the fruits of the Hazel (Corylus), the Asparagus, and Helios- 

 ciadium. In Note 48 I have referred to the cases of the Oak and the 

 Hazel ; and, indeed, we have only to examine the beach-drift in various 

 parts of the world, and to look at their respective stations, to learn that this 

 is not an effective mode of dispersal. Buoyancy of seed or fruit is only 

 one of many other qualities that is concerned with distribution by currents. 

 Nature does not act in this way in seed-distribution, and there can be 

 little doubt that the author of the Origin of Species would have been the 

 first to abandon this view, if his researches had been continued. It should 

 be especially noted that plants of the sea-beach, where the floating power 

 happens to be //, or limited only to a week or two, would have derived 

 great advantage from the drying of their seeds or fruits if it was really 

 effective in aiding dispersal by currents. However, with plants like 



