“Maternal apomictic embryos develop from a somatic cell within the ovule or from an unreduced embryo sac derived from the megaspore mother cell.”

“Arborescent lycopsids began life as an embryo germinating from an indehiscent megaspore.”

“In sexual reproduction a diploid somatic cell, the megaspore mother cell, undergoes meiosis to produce four reduced megaspores.”

“In angiosperms, or flowering plants, by contrast, the seeds are enclosed during development in a structure variously termed a pistil or a carpel, which is sometimes considered to represent an enfolded megasporophyll.”

“Pea and bean plants, exemplifying the simplest situation, show in each flower a single pistil, traditionally thought of as a megasporophyll or carpel.”

“The pollen in angiosperms is transferred to the surface of the megasporophyll, whereas in gymnosperms it is brought to the micropyle of the ovule itself.”

“In Selaginella, usually only four large megaspores are produced in a megasporangium.”

“As in other gymnosperms, the ovule consisted of one megasporangium within a single integument.”

“The number of microspores produced is very large, but only four megaspores are borne in each megasporangium.”

“The formation of the female gamete can be subdivided into two stages, megasporogenesis and megagametogenesis.”

“The reduction in cell number of the female gametophyte and embryo allows a large number of megasporogenesis events to occur in the ovary.”

“Female sterile plants are ideal for isolating genes involved in megasporogenesis and for investigating gene functions.”