[Spermatogenesis in a pteridophyte. 1. First stages of the motile apparatus]

The first appearance of the motile apparatus can be seen just before the last spermatogenous division. It is a granular cluster of electron dense material which sends out arms which are transformed into spindle-microtubules. After division, the latter disappear, and procentrioles differentiate in a blepharoplast from the material of the 'organizing centre' from which are successively born two different systems of microtubules. In addition, the motile apparatus is initiated in the cytoplasm away from the nucleus. It is only later that the centrioles are intimately combined with the nucleus through the medium of the microtubule ribbon, thus marking a fist stage in the maturation of the spermatozoon.