426 A NATURALIST IN THE PACIFIC chap. 



dangling in the air from a pin's point. I suppose that this is 

 connected with some hj'groscopic quaHty. At all events, it would 

 enable these light seeds to be carried about not only by birds and 

 bats but also by insects. It is possible that man has aided in the 

 dispersal of this interesting plant ; but birds, bats, and insects have, 

 I think, mainly done the work. 



LUFFA INSULARUM 



This is regarded as a maritime form of Luffa cylindrica, a plant 

 commonly cultivated throughout the tropics. The South Pacific 

 plant, which occurs also in Australia and Malaya, has been found 

 in New Caledonia, Fiji, Tonga, Rarotonga, and Tahiti. In Fiji it 

 grows chiefly on the "talasinga" plains and in places once under 

 cultivation. I noticed it in one locality climbing over the branches 

 of an Inocarpus tree on the banks of the Rewa. In Rarotonga it 

 is common in the lower regions. It is, according to Nadeaud, fairly 

 frequent on the shore and in the lower valleys of Tahiti, where it 

 was collected by Banks and Solander, the companions of Cook. 

 The Pacific islanders, as far as can be gathered, make little or no 

 use of the plant ; and unless it was introduced accidentally with 

 their cultivated plants, they could scarcely have been concerned in 

 its dispersal. 



In Fiji I made a special point of investigating the mode of 

 dispersal of this plant. The fruits, which ultimately become dry 

 and fibrous, are to be seen hanging vertically from the plant as it 

 climbs among the branches of a tree. The apical disk usually falls 

 off, and many of the seeds drop out through the hole thus produced ; 

 but a few remain entangled in the fibrous material occupying the 

 interior of the fruit. I have noticed such fruits floating down the 

 stream of the Rewa River ; but my experiments showed that they 

 do not float more than a week, whether in fresh or salt water. The 

 seeds, however, possess a hard, impervious shell, and are well 

 adapted to withstand unharmed prolonged immersion in the sea. 

 They will evidently float for months. Out of one hundred selected 

 seeds placed in sea-water, sixty were found afloat and sound after 

 two months. The cause of the seed-buoyancy is purelj'- mechanical. 

 Neither the shell nor the kernel has any floating power, the 

 buoyancy arising, as with Convolvulaceous seeds, from the unfilled 

 space in the seed-cavity. When in Fiji, I tested the seeds of the 

 ordinary cultivated tropical form of the plant which had been 



