The reproductive means of the Aesculus hippocastanum can be summarized by the three "Fs": The structure and function of the flower, the fertilization process, and the fruit form and function. 

Flowers are the main reproductive organ of any angiosperm.  In the horse chestnut, the flowers are arranged in inflorescences.  This means that multiple flowers are grouped together into clusters.  Each flower contains stamen, carpel(s), sepals, and petals.  Sepals protect the bud before it blooms and the petals attract pollinators to the flower. Horse chestnut petals are white with red and/or yellow centers. Each stamen consists of a pollen producing anther atop a supportive filament.  The pollen contains the male gametophyte of the plant. Each carpel consists of a sticky stigma connected to an ovary containing ovules by a slender neck called the style.  The ovule is the sight of the development of the female gametophyte in the plant.
Pollen can be transported for the anther to the sticky stamen in a huge variety of ways.  These methods of transfer can be divided into two different types, abiotic and biotic.  The majority of angiosperms rely heavily on the biotic factors, such as through bees, moths, birds, flies, and bats.  However, horse chestnuts are known to rely on the only major abiotic method; wind.  They make up for the inefficiency of wind-dissemination by creating a large quantity of flowers and consequently pollen. 

The development of the male gametophyte occurs primarily within the anther.  The anther begins by containing diploid microsporocytes.  These cells undergo meiosis to produce four haploid microspores.  Each of these cells develop into a pollen grain.  After the pollen grain lands on the stigma of the carpel the male gametophyte within will divide its nucleus to create two sperm.  The development of the female gametophyte occurs within the ovule.  The ovule starts by containing a megasporocyte, otherwise known as the megaspore mother cell.  This undergoes meiosis to give rise to four haploid cells, much like the male gametophyte development.  However, only one of these will develop into the megaspore and the others simply disintegrate.  This megaspore then undergoes mitotic division three times without any type of cytokinesis.  This results in a very large cell with eight haploid nuclei.  Membranes then form to fully develop this into the embryo sac.  This mature embryo sac contains one egg, two synergids to guide the pollen, three antipodal cells, and two polar nuclei. 
This sets the stage for the fertilization that occurs.  The synergids attract the sperm down the style to the ovule containing the egg.  At this point one sperm fertilizes the egg producing a dipoid zygote.  Then what is the other sperm for? This combines with the two polar nucli inside the ovule.  This creates a tripoid cell to eventually give rise to the endosperm.  Because of this two sperm fertilization, this process is coined double fertilization. 

The horse chestnut fruit presents with a spiny exterior containing 1-3 seeds or conkers.  Within this fruit the triploid cell in the ovule develops into the endosperm before the embryo develops.  Then the zygote begins developing into an embryo within the two cotyledons that eventually develop into the first leaves of the tree.  As this is such an important part of the plant, plants utilize many methods to spread these seeds far and wide.  Some methods of dispersal is via water, wind, and animals.  The horse chestnut potentially uses all of these methods except for wind.  Though wind could have a small impact on the end location of the seeds, it would have very little effect on the heavy seeds produced by the horse chestnut.  Therefore, if the trees are not placed by a body of water, they primarily spread their seeds through animals. 


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