IX THE GERMINATION OF FLOATING SEEDS 79 



may contribute to river-drift. Such trees may grow on the banks 

 of the estuary, and their fruits would thus readily fall into the 

 water ; but in the Rewa estuary in Fiji it was evident that the 

 fruits and seeds of beach-plants, such as Scaevola Koenigii, are also 

 brought in by the tide. The seeds of Morinda citrifolia were 

 often noticed in the Rewa drift together with the fruits of Heritiera 

 littoralis, which is both a beach and a swamp plant, but never in a 

 germinating condition. The same remark applies also to the 

 fruits of beach trees found afloat in the sea between the islands, 

 such as Cordia subcordata, Guettarda speciosa, and Terminalia. 

 It is possible that a few of these plants, as in the case of Bar- 

 ringtonia speciosa, display traces in the structure of their fruits of 

 a lost viviparous habit. (See Note 50.) It is pointed out in 

 discussing Guettarda that germination is much more easily induced 

 than one would expect in the case of fruits with such a hard 

 ligneous putamen. 



An interesting subject is presented in the abortive germination 

 of the floating seeds of many plants of the Leguminosae and 

 Convolvulacese both at sea and in a tropical estuary. My con- 

 clusions on this matter are based partly on observations made in 

 Fiji, but mainly on the results of numbers of experiments, this 

 being unavoidable, since the abortive germination causes the 

 sinking of the seed. The principal determining cause of the 

 germination in water of one of these floating seeds is evidently to 

 be sought in the temperature of the water, it being immaterial for 

 the earliest stage of germination, as many of my experiments 

 indicate, whether the seed or fruit is afloat in the sea or in the 

 river. In these flotation experiments, when conducted under warm 

 conditions with sea-water, the earliest signs of germination were 

 frequently displayed in the softening, swelling, and sinking of the 

 seed. If the swelling seed is taken out in time and planted after a 

 preliminary soaking in fresh water, the germinating process is at 

 once resumed and is often successfully and rapidly completed ; but 

 if the seed is allowed to remain in the vessel after it has absorbed 

 sea-water the vitality of the embryo is destroyed and the seed 

 decays. 



That many seeds would fail from this cause to cross an ocean 

 my experiments repeatedly demonstrated. Nor does the ap- 

 pearance of a seed afford any indication of its probable failure to 

 cross an ocean. Some seeds of Mucuna, as far as their hard 

 coverings could guide one, would seem to be quite secure from 

 such a risk. The stony seeds, for instance, of M. urens D.C. look 



