It is true he does not say whether this name applies to the white mulberry, _pe-sang_, of the Chinese plantations.[730] The antiquity of its culture in China,[731] and in Japan, and the number of different varieties grown there, lead us to believe that its original area extended eastward as far as Japan; but the indigenous flora of Southern China is little known, and the most trustworthy authors do not affirm that the plant is indigenous in Japan. Franchet and Savatier[732] say that it is “cultivated from time immemorial, and become wild here and there.” It is worthy of note also that the white mulberry appears to thrive especially in mountainous and temperate countries, whence it may be argued that it was formerly introduced from the north of China into the plains of the south. It is known that birds are fond of the fruit, and bear the seeds to great distances and into uncultivated ground, and this makes it difficult to discover its really original habitat. This facility of naturalization doubtless explains the presence in successive epochs of the white mulberry in Western Asia and the south of Europe. This must have occurred especially after the monks brought the silkworm to Constantinople under Justinian in the sixth century, and as the culture of silkworms was gradually propagated westwards. However, Targioni has proved that only the black mulberry, _M. nigra_, was known in Sicily and Italy when the manufacture of silk was introduced into Sicily in 1148, and two centuries later into Tuscany.[733] According to the same author, the introduction of the white mulberry into Tuscany dates at the earliest from the year 1340. In like manner the manufacture of silk may have begun in China, because the silkworm is natural to that country; but it is very probable that the tree grew also in the north of India, where so many travellers have found it wild. In Persia, Armenia, and Asia Minor, I am inclined to believe that it was naturalized at a very early epoch, rather than to share Grisebach’s opinion that it is indigenous in the basin of the Caspian Sea. Boissier does not give it as wild in that region.[734] Buhse[735] found it in Persia, near Erivan and Bashnaruschin, and he adds, “naturalized in abundance in Ghilan and Masenderan.” Ledebour,[736] in his Russian flora, mentions numerous localities round the Caucasus, but he does not specify whether the species is wild or naturalized. In the Crimea, Greece, and Italy, it exists only in a cultivated state.[737] A variety, _tatarica_, often cultivated in the south of Russia, has become naturalized near the Volga.[738]