Spiral Thickenings of Vessel Elements in Magnoliaceae in China

Spiral thickenings in the inner walls of vessels were studied in 10 genera 69 species of Magnoliaceae in China under scanning electron microscopic observation. Spiral thickenings were found in some species. The majority of these species showed complete thickenings of the inner wall, however, in some of which the spiral thickenings were less obvious at both ends. In others, these spiral thickenings existed only in the middle portion, uniformly or irregularly distributed.