IX THE GERMINATION OF FLOATING SEEDS 8i 



where the water-temperature ranged for the first few weeks 

 between 75° and 90°, three of them began to swell within ten days, 

 and on removal at once germinated healthily. The remaining two 

 were afloat at the end of twelve months, and when planted one of 

 them germinated a month afterwards. 



Having experimented on the seeds of about half a dozen 

 different species of Mucuna in sea-water, all with buoyant qualities, 

 it is possible for me to lay down the general rule for the buoyant 

 seeds of the genus that sinking is the result of an attempt at 

 germination, which, as before observed, proves abortive unless the 

 seed is removed in time. It is obvious that the gardener wishing 

 to raise plants of this genus without delay might profitably adopt 

 the method of keeping them afloat in water at a temperature of 

 80 — 90° F. until they begin to swell, which may happen in some 

 cases in a few days. Sea-water seems to produce the most rapid 

 results. 



When on Keeling Atoll in the Indian Ocean I collected, 

 amongst the stranded seed-drift brought by the currents to those 

 islands, the seeds of five or six species of Mucuna, two of which 

 were identified at Kew as M. macrocarpa, Wall., and M. gigantea 

 D.C. (see my paper on the dispersal of plants at Keeling Atoll). 

 No plant of this genus appears up to that time to have been 

 recorded from the Keeling Islands, so that at all events most if not 

 all of the seeds had been brought by the currents from the Indian 

 Archipelago, some 700 miles away. It may be added that amongst 

 the drift gathered by me on the south coast of Java the seeds of 

 three species of Mucuna were identified at Kew, including the two 

 above-named species from Keeling Atoll. 



These current-borne seeds of the Keeling beaches had probably 

 performed an ocean journey of a thousand miles, since the route 

 could scarcely have been direct. Yet their behaviour when placed 

 eighteen months after in sea-water in a hothouse in England was 

 most erratic. Of three seeds of Mucuna gigantea all swelled and 

 sank within eight days. Two seeds of M. macrocarpa sank after 

 floating from sixty to a hundred days ; whilst of two seeds of 

 another species both remained afloat after a year. In a sea-water 

 experiment in England on five Hawaiian seeds of M. gigantea, 

 under the conditions referred to in the Mucuna urens experiment, 

 one sank within ten days, whilst three of them were afloat after 

 twelve months, one of them subsequently germinating. This 

 species, it may be remarked, is widely distributed as a coast plant 

 over tropical Asia, Australia, and in Polynesia. It seems to take 

 VOL. II G 



