INTRODUCED PLANTS AND ANIMALS. 283 



nate. To hasten geniiiiialiun the seeds are sometimes carefully rasped on 

 either side with a file. The tree is of rapid growth, thriving best in a moist 

 climate. The natural home of the species however, is in the drier regions of 

 Brazil. It is closely related to the Cassava, mentioned elsewhere, and belongs 

 to the spurge family, which also includes the Para ^^ and many othei- rubber- 

 producing plants. The latex or milky sap occurs in the leaves, stems and 

 trunk. There is a continuous network of milk-tubes all through the living 

 green portion of the liark of the tree. The latex is collected by various 

 methods of tapping, and from this gum-like mass the rubber of commerce is 

 refined. 



While the earlier plantings were largely of the foregoing species, there is 

 considerable area being planted to Hevea. Both species belong to the 

 Eupliorhiacece. They and their near relatives may be distinguished from 

 other rubber-producing plants by the hard, flinty seeds and the palmate leaves, 

 resembling those of the horse-chestnut. Such latex-producing trees, belong- 

 ing to the banian family, as the Assam rubber,!*^ the pipul tree, or banian 

 fig,i' are well established. 



To the list of introduced species must now be added the Hawaiian rubber 

 tree^'^ brought to the attention of the Hawaiian Experiment Station in 1912 for 

 investigation. Its latex-producing characteristics were noted by a chance dis- 

 covery in the Kona district on Hawaii, where there are several thousand 

 acres of this promising tree. The natives were long familiar with its gum- 

 like latex and gave to the tree the name koko or akoko, in allusion to the 

 milk-sap which exudes freely from the injured bark. The fact that it is a 

 conspicuous tree, often twenty-five feet high, with a trunk ten inches in 

 diameter, and that it occurs in more or less extensive areas on several islands 

 of the group ; and, furthermore, that it has long been known to botanists, hav- 

 ing been described as a sub-species by Dr. Gray many years ago, indicates 

 how little attention has been given as yet to the investigation of the native 

 flora from the economic standpoint. The tree belongs to the typical tribe ^'-^ 

 of euphorbias in which the flowerhead resembles a single flower. The species 

 has the flowerhead almost sessile and is marked by having small linear leaves 

 with the veins oblique to the rib. So far as its latex-producing qualities have 

 been investigated, the koko seem to give much promise as a rubber-yielding 

 plant. Its discovery points to the wisdom of extensive investigation of this 

 and other economic plants native to the islands, as well as those of promise 

 from other lands that may be suited to Hawaii's soil and climate, with a view 

 to the establishment of economic species in much of the island Territory now 

 given over to cattle ranges, or classed as waste land. 



Tobacco. 



Climate and soil are thought to have a mai'ked influence on the (|uality of 

 tobacco,-*^ and experiments that have been conducted in the islands in recent 



^^ Bevea Braziliensis. '* Ficvs elastira. ^'^ Ficiis religiosa. ^^ Eupliarhid lorifoHa. 



^^ Eiiphorbieoe. -" yicotiana Tahncum. 



