the multideck ship at the back groud( in China) is only 35 meters long. Zheng He's hsip was 150 meters in length. that could be the reason why they planted fruits, vegetables on the top deck in those huge ships. They prevented Beri Beri and many other sickness. They were good in preventive medicine ? ! Sing and features of Maize and Tobacco grown around southern china back dated to 5 to six hundred years ago is interesting and link to the indirect proof of Zheng He navigated to America and got Maize and Tobacco plant. ( They could have planted on top of the ship on their way back to China.