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gradually improved southwards, owing to the richer contents 

 of saccharine principles. Besides, the colour deepens artd the: 

 rind tends to become more and more smooth, accompanied by; 

 the diminution: of its thiclcness. Finally, in Riukiu Isles and 

 Formosa, the sugary contents entirely replace the acid sub- 

 stances. It becomes simply very sweet and thus the true 

 flavour of the fruits are rather lost. The distribution of our 

 citrous fruits seem mainly influenced by the average minimum- 

 temperatures of- tlie winter months. According to the Observ- 

 ations of the Central Meteoi^ological Observatory, the north- 

 limits of the hardiest kinds seem to coincide more or less per- 

 fectly with the winter isothermal of 3 degrees C, and those of 

 more tender species, as citrons and lemons arc' roughly- coiri~ 

 cident with 5 degrees C. winter isothermal. 



Of the many kinds, mandarins, Natsiidaidai and oranges 

 are the most ejctensively cultivated, the two latter being rEtther 

 recent introductions. They attain the highest perfection only 

 in south Japan, Of the sweet oranges, Washington Navel and' 

 Thomson's Improved are exclusively planted on a large scale.' 

 Many of the groves are young and a few have beerv' 

 iruiting for several years. In ■ my opinion, the sweet 

 oranges are difficult to grow in our humid atmosphere, 

 and the soils of south Japan, where the mandarins reach- 

 perfection as to the quality and yield, do not seem to be suited 

 to them. In America, it is known that the orange fails in 

 Florida, and succeeds in California, while the mandarin, which, 

 flourish in Florida, can not be cultivated with success in 

 California. -The climates of Florida and our south have a 

 certain similarity though they differ in degree. More over, 

 the famous orange regions of the world and the natural 

 habitat of the plant, for example, the Mediterranean countries, 

 Bahia in Brazil, and California, have something in common 

 in their cliniatic conditions. In other words, these are regions' 

 of moist winter and dry summer; oecologically the so-called 

 SclerophiloiiS wood-land climate! • . ■ 



