546 A NATURALIST IN THE PACIFIC 



The ultimate test of the capacity for germinating in sea-water seems to 

 lie in the behaviour of the seedling when left in the sea-water. Unless it 

 belongs to a characteristic plant of the salt marsh or of the estuary, like 

 Salicornia, it makes but little attempt at growth whilst afloat in sea-water, 

 showing no rootlets, though at times developing the plumule. 



The germination of seeds in sea-water also attracted the notice of 

 Darwin ; but his results in some respects are scarcely those I should have 

 looked for {Gardener's Chronicle, May, 1855, undjourn. Linn. Soc.,vo\. i., 

 p. 130, 1857). Out of the seeds of 87 plants placed in sea-water to test 

 their capacity of germination when afterwards planted, in three cases, those 

 of Tussilago farfara. Convolvulus tricolor, and the garden Orache (Atriplex), 

 the seeds germinated under the water, the freed seedlings, as with the two 

 first named plants, living in the sea-water for some time after. Darwin was 

 evidently himself surprised at these results, and I am quite unable to under- 

 stand them. In England and in the tropics I have carried on prolonged 

 sea-water experiments on the seeds of at least fifteen species of Convolvulus 

 and Ipomea (including the beach plants C. soldanella and I. pes caprse) and 

 have never obtained such a result. The seeds will nearly always germinate 

 well in fresh water ; but in sea-water the process begins, as indicated by the 

 swollen seed, and then aborts, the embryo dying (see page 83). The seeds 

 ot Atriplex patula, though a long time in sea-water in my experiments, made 

 no attempt to germinate there. Neither Prof. Martins, who experimented 

 upon the effects of sea-water immersion on the seeds of nearly 100 plants, 

 including many coast species, nor M. Thuret, who experimented in sea- 

 water on the seeds of 251 plants, the experiments being in some cases 

 prolonged for more than a year, make any reference, as far as I could 

 gather from their writings, to any cases of germination in sea-water. 

 Darwin's results, however, are always significant in matters of dispersal; 

 and perhaps one of my readers will be able to experiment again on his 

 three plants. 



When in Hawaii, I made some observations on the germination of 

 Batis maritima in sea-water, a plan with which I was also familiar in its 

 home in the salt-water pools of the coast of Peru. The mature fruits, on 

 being freed from the parent plant in sea-water, float away, and in from one 

 to two weeks they break down from decay, setting free the seeds. The 

 seeds float in sea-water indefinitely, their buoyancy only terminating with 

 their germination, the first seeds germinating afloat about six weeks after 

 the breaking down of the fruit, whilst the rest continue to float in the sea- 

 water during the next three months, some of them germinating at intervals, 

 and all of them doing so eventually. Strange to say, although the seedlings 

 remained healthy whilst afloat in the sea-water, they made no effort either 

 to separate the cotyledons or to produce a plumule. 



