XXVIII GYROCARPUS JACQUINI 423 



attains a great size ; and its abundance is implied by his remark 

 that he had to fell many trees to collect the fruits. 



The singular fruit, which has two long wings and looks like 

 a shuttlecock, dries up on the tree ; and in course of time it is 

 detached and falls to the ground. The falling fruit in its descent 

 twists round like a screw, and hence the Fijians call the tree the 

 Wiri-Wiri tree, the same name in the form of Wili-Wili being given 

 for a similar reason to Erythrina monosperma in Hawaii. Schimper 

 (p. 157) truly remarks that the fruits are too heavy to be carried 

 by the wind across a wide extent of sea ; and I ascertained by 

 experiment that in an ordinary trade-breeze they would only be 

 carried a few paces. Birds are quite out of the question as agents 

 of their transport to oceanic islands. We are driven then either to 

 the agency of man or to that of the current. The trees grow 

 rapidly and the timber is soft and perishable. The fruits are not 

 edible, and as far as I could ascertain the tree is of little or no 

 value to the Pacific Islander, there being at all events no reason to 

 believe that he has distributed it. 



We appeal lastly to the currents, the agency which Mr. 

 Bentham selected on a priori grounds (Presidential address, 

 Linnean Society, 1869). My experiments in Fiji showed that the 

 fruits, when dried on the tree and afterwards detached, are able to 

 float over long distances in sea-water. After two months they were 

 still afloat, the seeds inside being dry and unharmed. The fruit's 

 buoyancy was tested in different conditions, either without the 

 wings, or with both wings, or with but one wing, and it was found 

 that the wings, which float for only a day or two by themselves, 

 lessen the buoyancy of the fruit. Of fruits with both wings 

 attached forty per cent, floated after two months, whilst of those 

 deprived of the wings all floated after two months. In the ordinary 

 course of flotation the wings in most cases break off" during the 

 first few weeks, and in the rough-and-tumble of current-transport 

 this would occur sooner, so that the floating power of most of the 

 fruits would not be much afi'ected. The cause of the buoyancy 

 in a structural sense belongs to the Convolvulaceous type. The 

 kernel has no buoyancy, but it incompletely fills the cavity of the 

 seed-vessel, the coats of which are quite waterproof, but have no 

 independent floating power. 



It is thus evident that like many other shore-trees Gyrocarpus 

 Jacquini is distributed by the currents. It is not unlikely that its 

 present sporadic occurrence in the Pacific islands may be due to 

 the gradual extinction of the tree in this region, either on account 



