Micromorphology of the seed coats in Begonia section Squamibegonia Warb.

Begonia seeds can be distinguished from all other angiospermous seeds by the presence of a ring of collar cells under the micropylar-hilar part of the seed, which acts as an operculum during germination. Moreover, the differences in size, epidermal pattern, form of the cells and sculpturing of the testa provide additional characters, which can be of use in the delimitation of species and sections of the genus. The recent circumscription of Begonia Sect. Squamibegonia Warb. by De Wilde is corroborated by the micromorphological characters of the seed coats. The seeds of the section are relatively large and characterized by the absence of clear cuticular sculptures and by a cleavage of the anticlinal walls. The loss of micromorphological ornamentation seems to be related with the change-over to a different dispersal strategy.