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An apple is the pome produced by a plant of Malus, a taxonomic genus in Rosaceae. The name also commonly refers to the cultivated tree. An apple's seed-bearing core develops from fused carpels, while surrounding floral tissues contribute to its fleshy edible structure. This is an accessory fruit, so identifying the entire flesh with the ovary alone misses part of its development.^{[ref] [ref]}

A crosswise cut exposes the seed chambers and the firmer tissue around them. A lengthwise cut connects that core with the stalk at one end and persistent floral parts at the other. Comparing an apple with a peach is instructive: the peach has a single conspicuous stone surrounding its seed, whereas an apple has several chambers formed by fused carpels.

The taxonomic genus includes trees cultivated for edible fruits and ornamental crabapples. A cultivar is a selected cultivated form, rather than an automatic synonym for a separate species. Differences in fruit size, color and texture can therefore occur within the cultivated material to which the everyday word apple refers.^[ref]

Bart J. Janssen studies the molecular control of plant development. A 2008 study led by Janssen followed gene expression as apple fruits developed, linking molecular measurements to recognizable changes in anatomy and growth.

The investigators collected samples at eight developmental times and used a DNA microarray representing approximately 13000 genes. Four broad temporal patterns distinguished flower stages, early cell division, growth with starch accumulation, and ripening. Selected measurements were checked using Quantitative PCR.^[ref]

An apple is a pome, with both an ovary-derived core and surrounding hypanthium tissue. Comparing stages therefore asks how growth of a composite fruit is coordinated. A gene whose expression peaks during cell division becomes a candidate for further investigation; matching the timing does not alone demonstrate that the gene causes that developmental change.^[ref]

A hypanthium is a cup-like or tubular part of a flower whose rim bears the stamens and perianth, including sepals and petals when both are present. It forms around the region occupied by the ovary. The shape of the cup and its relationship to the ovary are separate features: a hypanthium need not be fused to the ovary along its sides.^[ref]

The apple provides a familiar consequence of this arrangement. During development of this pome, tissues around the ovary enlarge into much of the edible flesh, while the ovary contributes the central core. A longitudinal slice therefore reveals more than the wall of a swollen ovary: it contains tissues derived from different parts of the original flower. This distinction matters when asking which tissues undergo cell division and which increase in cell size during fruit growth.^[ref]

An inferior ovary is an ovary lying below the level where the perianth and stamens attach, with the surrounding floral tissue fused to it apart from, potentially, a free summit. Epigyny describes the corresponding position of the other floral parts above the ovary. “Inferior” specifies this anatomical relationship, rather than the direction in which a flower happens to point.^[ref]

To identify the arrangement, inspect a lengthwise section through a flower and trace the sepals, petals and stamens to their attachment around the ovary. Merely seeing a cup-shaped hypanthium is insufficient: a superior ovary can stand freely inside such a cup. The attachment and fusion must be checked together.^[ref]

An apple develops as a pome from an inferior ovary; its mature core and surrounding flesh retain the consequences of that floral construction.^[ref]

Malus is the taxonomic genus of apples and crabapples in Rosaceae. Its members are deciduous shrubs or trees. Their flowers have numerous stamens and several fused carpels; the mature fruit is a pome, with fleshy tissue surrounding the seed-bearing core. The genus name covers related wild and cultivated plants, whereas an individual cultivar identifies a selected cultivated form.^[ref]

A useful identification exercise follows one flower into one fruit. A transverse cut through a familiar apple exposes the chambers of the core; a longitudinal cut connects them to the stalk and persistent floral parts. The firm chamber walls and the surrounding flesh are distinguishable tissues. Comparing them with the single hard stone of a peach connects differences in mature fruit to differences in carpel arrangement.

Small ornamental crabapples and large eating apples can both belong to Malus. Size or culinary use alone therefore does not define this taxonomic genus. Floral and fruit structure provide a biological comparison across plants selected for very different purposes.^[ref]

A pome is a fleshy accessory fruit developing from an inferior ovary, with an enlarged hypanthium surrounding the central fruit tissues. An apple is a familiar example. Much of its edible flesh comes from tissue around the ovary, whereas the central core corresponds to the developed ovary. Thus the fleshy part of a pome cannot simply be identified with the pericarp, the wall derived from the ovary.^[ref]

To see the distinction, cut an apple lengthwise through its stalk and centre: locate the seeds, the enclosing core and the surrounding flesh. The fruit integrates structures with different developmental origins.

In a 2008 study, Bart J. Janssen and colleagues sampled developing apple fruits at eight times and used a DNA microarray representing roughly 13000 genes. They identified coordinated gene expression patterns associated with early cell division, later growth and starch accumulation, and ripening. The experiment illustrates how the anatomy of a pome motivates a molecular question: how are growth and maturation of its different tissues coordinated?^[ref]

Rosaceae is the flowering plant family containing roses, apples, peaches and strawberries. It includes herbs, shrubs and trees, so a shared growth habit is not its defining feature. Its flowers typically have five petals and a hypanthium, a cup or platform associated with the attachment of floral parts. The number and arrangement of carpels, and their relation to the hypanthium, vary substantially across the family.^[ref]

The family's fruits make an illuminating anatomical comparison. A peach is a drupe, with flesh surrounding a hard stone that encloses the seed. An apple is a pome, in which tissues surrounding the seed-bearing core contribute much of the edible flesh. In a strawberry, the enlarged receptacle carries many small dry fruits on its surface. A familiar edible object can therefore involve different parts of the flower, rather than always being one enlarged ovary.^[ref]

For a practical comparison, cut each fruit lengthwise and locate the seeds before identifying the fleshy tissue. This observation connects the mature structure back to the arrangement of carpels and surrounding floral tissue. Fruit type is useful evidence within Rosaceae, while variation in that type is compatible with membership in one evolutionary family.