Bell P R
J Cell Sci. 1981 Oct;51:109-19. doi: 10.1242/jcs.51.1.109.
Megasporogenesis in the heterosporous fern Marsilea (Hydropterideae) shows features intermediate between sporogenesis in homosporous ferns and that in heterosporous seed plants. The plastids in the dyads and young spores were associated with tubules 30-35 nm in diameter, probably a specialized form of endoplasmic reticulum. No consistent differences in size or cytoplasmic components could be found between the megaspores of a tetrad that might account for differential survival. The view that megaspore viability within the tetrad is genetically determined is thereby strengthened.
异型孢子蕨类植物田字草（水蕨科）的大孢子发生表现出的特征介于同型孢子蕨类植物和异型孢子种子植物的孢子发生之间。二分体和幼龄孢子中的质体与直径为30 - 35纳米的小管相关联，可能是内质网的一种特殊形式。四分体中大孢子之间在大小或细胞质成分上未发现一致的差异，而这些差异可能解释不同的存活率。因此，四分体内大孢子活力由基因决定这一观点得到了加强。
