tube cell

(tube nucleus) One of the cells contained within the microspore of gymnosperms, the others being the generative cell and the prothallial cell or cells. In Cycas it enters the haustorial pollen tube but its function is uncertain. In angiosperms the cell at the tip of the pollen tube that precedes the generative nuclei is sometimes termed the tube cell but it is more often called the *vegetative nucleus.