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An angiosperm with flowers arranged in an umbel.^[ref]

A plant that produces flowers and encloses its ovules within an ovary.

An angiosperm with small flowers on a spadix enclosed by a greenish spathe.^[ref]

A flower containing both male and female reproductive organs, stamens and carpels. It differs from monoecy, in which male and female structures occur separately on the same individual.

A modified leaf associated with a flower or inflorescence.

An undeveloped shoot or flower, often enclosed by protective leaves.

The outer envelope of a flower, composed of sepals.

A female reproductive unit of a flower, comprising a stigma, a style and an ovary. A flower may have several carpels, including fused ones.^[ref]

The petals of a flower, collectively.

Transfer of pollen between different individuals of the same species; compare self-pollination.^[ref]

A flower can contain both reproductive groups and still receive pollen from another individual. Conversely, transfer between two flowers on one plant does not by itself imply cross-pollination. Following the donor and recipient individuals makes pollination useful for studying genetics: organ position alone cannot identify whose alleles meet at fertilization.

Temporal separation of male and female reproductive function. It can reduce self-fertilization without requiring separate male and female flowers.

The organization of symmetry in a flower. Whole-flower symmetry, individual organ shape and developmental identity are distinct characters; similar outlines can arise through different molecular mechanisms.

A small flower, especially one forming part of a dense inflorescence such as a flower head.

A flower is an angiosperm's reproductive structure. Stamens produce pollen; carpels enclose ovules. Petals and sepals surround these organs in a complete flower, but some flowers lack one or more groups, including either reproductive group.^[ref]

Read the drawing from outside inward, then trace two routes: where pollen is released, and where an ovule is enclosed. This reveals why catching pollen and forming a seed require different structures. A detached petal cannot substitute for a stigma simply because both belong to the same flower.

An inflorescence of closely packed flowers on a common expanded support, as in the common daisy.

Spatial separation of male and female reproductive organs that can reduce self-pollen transfer while retaining them within one flower.

Independent assortment means that transmission at different genetic loci has conditional independence given the parental genotype. With fair Mendelian segregation, a parent heterozygous at two genetic loci, $AaBb$, produces $AB,Ab,aB,ab$ gametes with probability $1/4$ each. For example,Here $AB$ labels an allele combination; it does not assert that the two genetic loci lie on the same chromosome.

The physical model is stochastic orientation of different homologous chromosome pairs toward the two poles of the spindle apparatus in meiosis I. One pair's orientation does not determine another's. For two pairs, one division can send $A,B$ together and $a,b$ together; another can send $A,b$ together and $a,B$ together. See The Process of Meiosis (§11.1, Metaphase I and Figure 11.5: random orientation of chromosome pairs).

With $k$ distinguishable homologous chromosome pairs, there are $2^k$ choices of parental homologous chromosome origin for a product at a specified pole, each with probability $2^{-k}$ under this model. For $k=3$, enumerate $MMM,MMP,MPM,MPP,PMM,PMP,PPM,PPP$, where M and P mark parental origins. Whole-pole reversal pairs complementary choices, leaving $2^{k-1}$ unordered partitions for $k\ge 1$. For $k=2$ there are four choices for a specified pole but only the two relative orientations drawn. This counts possible products across meioses, not eight different products of one division when $k=3$. Identical alleles at scored genetic loci can also make different parental-origin choices observationally indistinguishable.

Independent assortment of different chromosome pairs does not imply independence of every pair of genes. Nearby genetic loci on the same chromosome can show genetic linkage. Chromosomal crossover can create new haplotypes, but does not automatically erase genetic linkage. See Laws of Inheritance (§12.3, Law of Independent Assortment and Linked Genes Violate the Law of Independent Assortment). In the ordinary fair two-locus model with parental haplotypes $AB/ab$ and recombination fraction $r$,Thus $r=0$ gives only the two parental haplotypes, while $r=1/2$ gives four equal probabilities. A recombination fraction of $1/2$ alone does not establish that the genetic loci lie on different chromosomes.

A motivating experiment appears in Experiments in Plant Hybridization by Gregor Mendel (§9, “The Reproductive Cells of the Hybrids”). In peas, hybrids for round versus wrinkled seeds and yellow versus green seeds were crossed reciprocally with constant wrinkled-green plants. The readout was visible seed shape and color: hybrid seed parents gave 31 round-yellow, 26 round-green, 27 wrinkled-yellow and 26 wrinkled-green; the reciprocal cross gave 24, 25, 22 and 27.

The apparatus was controlled pollination: opening immature flowers, removing stamens with forceps, and applying selected pollen to the stigma. Two-year trials established constant parental characters; greenhouse pots checked interference from insects in outdoor beds. Reciprocal crosses tested both transmission directions. These procedures are described in Experiments in Plant Hybridization by Gregor Mendel (§§2–3).

With complete dominance at both genetic loci, this test cross makes each phenotype report one hybrid gamete combination. The ideal expected values are $110/4=27.5$ and $98/4=24.5$ per class. The observations support four transmitted combinations, approximately equally frequent. They do not directly image chromosome orientation or prove independence for all genes; failed development and seed germination also limit the inference, as §9 notes.

The arrangement of flowers on a flowering axis, or the flowering system itself.

A ring or several rings of bracts surrounding a flower or inflorescence.^[ref]

Occurrence of separate male and female reproductive structures on one individual. It does not mean that each flower is bisexual.