200 THE PLANT WORI.D 



doubtful whether rubber of requisite quality and in quantities needed for 

 commercial exploitation can be extracted. lyike our milkweed and osage- 

 orange, this tree no doubt contains a rubber-like principle which will ap- 

 pear after a reasonable amount of coaxing and a considerable expenditure 

 of time, but after all scarcely worth the search. Mr. R. H. Biffin, who 

 has examined the phenomena of coagulation in the latices of a number 

 of plants, obtained the following results with that of the breadfruit : 



When diluted and centrifugalized it separates readily, giving a creamy 

 white layer which dries to a resinous mass somewhat resembling gutta- 

 percha. At the ordinary temperature this is quite hard and brittle, but 

 if the temperature is raised slightly it becomes plastic, and at the tem- 

 perature of boiling water it is soft and excessively sticky. The substance 

 is soluble in carbon bisulphide, and insoluble in water and alcohol." * 



From this it becomes apparent that unless superior methods of extrac- 

 tion and treatment for its gum are found, the breadfruit will scarcely 

 enter into competition with any of the commercial rubbers. Experiments 

 recorded by Watt with the milk of the jak (A. integrifolia) were, however, 

 more promising in that the rubber prepared from its gum was leathery, 

 waterproof, and capable of removing pencil marks, thus fulfilling at least 

 the requirement which gave rubber its name. 



The breadfruit trees throughout Porto Rico are scarred with machete 

 marks made by the natives for the purpose of obtaining milk, which they 

 boil with coconut oil to obtain the thick, gummy substance used in 

 caulking canoes and rendering bottles water-tight ; this is also used 

 as a bird lime before it hardens. The milk is used as a medium for 

 paint in the Pacific islands, serving its purpose well, although for in- 

 teriors it does not give as smooth a finish as paint prepared with oil. 



NUTRITION. 



When obliged to compete with the banana as a food staple the bread- 

 fruit has taken second rank on account of its comparatively inferior yield 

 and slower growth ; in the West Indies the banana played an important 

 part in the cuisine of the explorers from the time of discovery, while the 

 aborigines had, in all probability, previously developed an extensive 

 acquaintance with that fruit, and accumulated traditions which were 

 passed on to their Spanish conquerors. Therefore when King George III 

 caused the breadfruit to be introduced into his West Indian islands in 

 1793, the banana had an overwhelming advantage in being already firmly 

 fixed in the list of traditional food-plants and the usual conservatism of 

 man in changing his food-materials prevented an extensive use of the 

 fruit in those islands. Except in a few of the Pacific Islands where the 

 successive ripening of different varieties of breadfruit keep it in season 



*Kew Bull. 14.0, pp. 177-181. August, 1898. 



