Anther

In an angiosperm, the terminal pollen sac of a stamen, where pollen grains containing sperm-producing male gametophytes form.

Basal Angiosperm

A member of one of three clades of early-diverging lineages of flowering plants. Examples are Amborella, water lilies, and star anise and its relatives.

Carpels

The ovule-producing reproductive organ of a flower, consisting of the stigma, style, and ovary.

Double Fertilization

A mechanism of fertilization in angiosperms in which two sperm cells unite with two cells in the female gametophyte (embryo sac) to form the zygote and endosperm.

Embryo Sac

The female gametophyte of angiosperms, formed from the growth and division of the megaspore into a multicellular structure that typically has eight haploid nuclei.

Endosperm

In angiosperms, a nutrient-rich tissue formed by the union of a sperm with two polar nuclei during double fertilization. The endosperm provides nourishment to the developing embryo in angiosperm seeds.

Fruit

A mature ovary of a flower. The fruit protects dormant seeds and often aids in their dispersal.

Integument

Layer of sporophyte tissue that contributes to the structure of an ovule of a seed plant.

Magnoliid

Member of the angiosperm clade that is most closely related to the combined eudicot and monocot clades. Extant examples are magnolias, laurels, and black pepper plants.

Micropyle

A pore in the integuments of an ovule.

Monocot

Member of a clade consisting of flowering plants that have one embryonic seed leaf, or cotyledon.

Ovary

In flowers, the portion of a carpel in which the egg-containing ovules develop.

Ovule

A structure that develops within the ovary of a seed plant and contains the female gametophyte.

Petal

A modified leaf of a flowering plant. Petals are the often colorful parts of a flower that advertise it to insects and other pollinators.

Pollen Grain

In seed plants, a structure consisting of the male gametophyte enclosed within a pollen wall.

Pollination

The transfer of pollen to the part of a seed plant containing the ovules, a process required for fertilization.

Sepals

A modified leaf in angiosperms that helps enclose and protect a flower bud before it opens.

Stamen

The pollen-producing reproductive organ of a flower, consisting of an anther and a filament.

Stigma

The sticky part of a flower's carpel, which receives pollen grains.

Style

The stalk of a flower's carpel, with the ovary at the base and the stigma at the top.