ABSTRACT
This chapter describes the stages in spermatogenous cell development and includes the development of bicentrioles in three anthocerote species. In somatic cells, and in spermatogenous cells up until the penultimate division, the microtubule organizing centre (MTOC) of the axial microtubule system and of the mitotic spindle is electron-opaque material from which the microtubules apparently emanate. The absence of microtubule arrays that determine the plane of subsequent cytokinesis in male gametophytic tissue is a character found throughout the land plants surveyed hitherto. With the advent of transmission electron microscopy, it was shown clearly that centrioles are present in the spermatogenous cells of a number of lower land plants. The spermatogenous cells then proceed to divide twice, using the pericentriolar material and the associated bicentrioles as the spindle MTOC. In the mosses and hepatics that have been studied, the bicentrioles apparently arise in an MTOC area and one pair of bicentrioles arises in this structure.
