RHODOPHYTA 105

Fig. 4.20 The behavior of the spermatium and its contents

during fertilization in a typical red alga. (Modified from

Wilson et al., 2003.)

moieties on the spermatangial appendages (Mine et al., 2003).

Meiosporangia and meiospores

Tetrasporangia, polysporangia, and bisporangia formed on diploid plants are generally regarded as being the seat of meiosis although there are exceptions to this. The tetrasporangia (Figs. 4.17(e), 4.18) form four tetraspores either in a row (zonate), crosswise (cruciate), or most commonly in a tetrad (tetrahedral). In the formation of tetraspores a wall is laid down inside the tetrasporangia by the protoplast, which has prominent dictyosomes (each dictyosome associated with a mitochondrion as is common in the Rhodophyceae; Kugrens and West,

1972b; Scott and Dixon, 1973b). The tetraspores are Fig. 4.21 The chemical structure of spermine. not joined by pit connections.