Zea mays is in Family Poaceae > Subfamily Panicoideae.
Maize is the internationally accepted name but it is commonly known as Corn.
The annual grass is very variable in many features including its size.
Typically the stems (culms) are around 1 to 2 m high.
The unbranched stems are solid and there may be rhizomes (underground stems) and basal prop roots.
The drooping alternate leaves are in 2 ranks on opposite sides of the stem (distichous).
One stem can have up to around 20 leaves.
Linear or lance-shaped blades are up to 1 m long and 10 cm wide.
The edges are often wavy and there are hairs with a nodular base.
With no petiole the blade bases run down the stem as a sheath.
At the top of the sheath is a 2 mm membranous ligule that may have hairs.
Plants are monoecious with separate male and female inflorescences on each.
Male inflorescences.
When the stem tip has produced all the leaves it will it converts to producing the male inflorescence.
This is a panicle up to 40 cm long with a stiff erect midrib.
Attached to the midrib are numerous racemes up to 20 cm long.
(Racemes have the lower flowers opening first.)
Along each raceme are 1 or more spikelets around 12 mm long.
Each flattened spikelet has a pair of bracts (glumes) at the base.
The broad glumes have a rounded tip with cilia (small hairs).
Each spikelet has 2 florets each with one male flower and 2 bracts.
One floret is on a short pedicel and the other has almost none.
Each floret has an outer lemma and an inner palea with those on the upper floret being smaller.
Male flowers are reduced to just 3 stamens with prominent yellow then red anthers.
Anthers release the wind blown pollen through apical pores.
Female inflorescences (ears) are in the leaf axils lower down the stem.
They are very variable even without considering all the hybrids available.
Each is a single raceme on a short or no peduncle.
They are tightly surrounded by long leaf-like basal bracts (spathes but called husks on corn).
The thick tough raceme midrib (cob), up to 20 or 30 cm long is cylindrical.
Running down the cob, and slightly sunken into it are 4 to 11 (8 to 30) rows of paired spikelets.
The compact flattened spikelets are around 10 mm long.
Each spikelet has a pair of wide bracts (glumes) at the base with cilia on the edges.
Spikelets have 2 florets with the lower sterile and the upper fertile.
Florets have one female flower and its lemma and palea bracts.
Female flowers are reduced to an inferior ovary with a style and stigma.
Just after the male flowers start releasing pollen the ovaries on the cob start growing long tubular styles.
Basal ones, up to 30 cm long take around 4 days to extend past the husks.
Collectively all the long pendulous styles form the silk.
The 2 linear stigmas on each style are exposed past the husks.
Pollen falling on a stigma germinates and sends a pollen tube down the tubular style to the ovary.
After fertilisation ovaries of fertile flowers develop into kernels.
The fruit are an indehiscent caryopsis with the ovary wall fused to the outer layer of the kernel.
Each cob typically has yellow or white kernels but there are other colours.
With modern plants the fruit no longer fall off the cob naturally so plants cannot reproduce on their own.
J.F.
