2009, Claire G. Williams, Conifer Reproductive Biology (page 74)The exine is composed of the two major layers: the outer sexine and the inner nexine. The inner nexine is further composed of nexine I and nexine II.
2012, Oswald Kiermayer, Cytomorphogenesis in Plants (page 366)Even though the period of nexine formation and the number and structure of the nexine layers vary, some general construction principles can be described. The nexine originates by deposition of sporopollenin onto lamellae ...
