544 A NATURALIST IN THE PACIFIC 



capacity of the fruits and seeds of several of the shore-plants above 

 mentioned, after long immersion in sea-water, are at times not to be 

 depended on for the flotation indications, the persistence of the seed's 

 vitality being the special purpose of his research. His negative results as 

 regards germination are not, however, always conclusive, since the period 

 employed from April to June was quite insufficient. In many of my 

 experiments seeds after long flotation in sea-water did not germinate for a 

 year or more afterwards. If his investigation had been extended, the 

 opinion that the Ranunculaceae, the Malvaceae, and the Convolvulace^e are 

 apparently least able to resist the action of sea-water would never have been 

 formed. A very large amount of evidence now shows that most seeds or 

 fruits that are at all well protected will germinate after long immersion in 

 sea-water. But all experiments must be well safeguarded and extended 

 over a year or two. The necessity of this was long since shown by Thuret. 

 By employing double sets of seeds he ascertained that in a third of the 

 species germination failed not only in the case of the seeds immersed in 

 sea-water, but also in those that had not been placed in sea-water at all. 

 Future investigators may, however, regard the buoyant qualities of seeds 

 or fruits with their associated structural characters as offering now the true 

 line of research. Observers beginning with Berkeley and Darwin down 

 to the present time have quite established the fact that seeds as a rule 

 germinate freely after long sea-water immersion. 



NOTE 19 (page 35) 



On Germination in Sea-water 



During my experiments on the buoyancy of about 270 British plants, 

 about a fourth of them (including most of those with buoyant seeds or fruits) 

 were subjected to prolonged immersion in sea-water from periods varying 

 from six to thirty-three months. If we except plants like Aster tripolium, 

 Salicornia herbacea, Triglochin maritimum, &c., that live normally in salt 

 marshes, or on the muddy banks of estuaries, only one of the whole number, 

 namely. Ranunculus sceleratus, displayed the capacity of germination in 

 sea-water. Amongst the plants that failed may be mentioned the follow- 

 ing that are confined to the sea-beach — Arenaria peploides, Cakile mari- 

 tima, Convolvulus soldanella, Eryngium maritimum, Euphorbia paralv.s, 

 Glaucium luteum, and we may here include Crithmum maritimum of 

 the rocky coasts. Of the beach-plants that also grow inland, Silene 

 maritima and Spergularia rubra (excepting the form found on muddy 

 coast flats) likewise failed. Amongst the plants of miscellaneous inland 

 stations that failed were Atriplex patula, Bidens cernua, B. tripartita, 

 Calla palustris, several species of Carex both from dry and wet situations, 

 Convolvulus arvensis, C. sepium, Hydrocotyle vulgaris. Iris pseudacorus. 



