The seed of Swietenia macrophylla is a wind-dispersed diaspore. The wing is formed by extension of the outer integument and has extensive air spaces. The cotyledons are fused in the upper 2/3, along the adaxial surface and, during the process of germination, they develop petiolar structures by intercalar growth at the base. Later, the petioles extend longitudinally and arch to the outside, allowing the enlargement and emergence of the epicotyl, enclosed between the cotyledons. Germination is hypogeous and cryptocotylar.