Ultrastructure of the Tricellular Pollen Grains of DiploidEuphorbia Dulcis

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Abstract
The generative cell divides into two irregular shaped sperm cells, with a sharp angle between them. A thin space separates the membranes of the two sperm cells from the membrane of the vegetative cell. This space is interrupted by cytoplasmic channels. The sperm cell cytoplasm contains small mitochondria with evident cristae, Golgi bodies with few plated cisternae, many free ribosomes, some vesicles and some small vacuoles. The nuclei at mature stage are multilobate and have many pores. Plastids are not present. At the sides of the pores the intine consists of an electrondense layer of compact fibrils. In the vegetative cytoplasm two types of RER are present. Around the vegetative nucleus and the sperm cells the cisternae are long. Short and sacculated cisternae surround the plastids. In the early stages of development also short RER cisternae surround the drops of lipid. At anthesis lipids are absent.