2. Formation of fruits and seeds:

Seeds are of two types:

a. Endospermic Seeds:

The embryo may keep the endosperm, the seeds in this case are called (Endospermic seeds) such as Monocotyledonous seeds, in which the integuments of the ovule and the ovary fuse together forming a single-seeded fruit (that is called a grain), as in Maize and Wheat.

b. Exendospermic Seeds:

The embryo may feed on the endospermic tissue during its development, so it is called (Exendospermic seeds) accordingly, the plant has to store another food in the cotyledons, hence these seeds are called Dicotyledonous seeds, where the integuments of the ovule harden forming the seed testa, it is called a seed. As in Beans and Pea seeds.

Events that take place after fertilization:

1. The Calyx, the Corolla, the Androecium, the Style, and the Stigma wither and fall out as their functions are terminated.

2. The ovary remains that stores food, ripens, and transformed into fruit due to the hormones (Auxins) secreted by the ovary.

3. The ovary's wall is transformed into the pericarp, and the seed wall into the coat (the seed testa).

4. The 2 synergid cells and the 3 antipodal cells disappear.

5. The micropyle remains so as to allow water to get into the seed during germination.

There are some fruits which keep some parts of the flower:

1. Leaflets of the Calyx and the Stamens remain in case of Pomegranate.

2. The Calyx may take part in fruit formation as in Egg plant, and Dates fruits.

3. The Corolla leaflets may stay on Marrow fruits.

False fruits:

It’s the fruit in which any part except its ovary enlarges storing food, as in Apple where the receptacle may share in the fruit formation.

Parthenocarpy:

It’s the fruit development naturally devoid of seeds since no fertilization takes place as in Banana and Pine-apple. Parthenocarpy can be carried out artificially by spraying the stigmata of flowers with the extract of pollen grains (pollen grains powder in ether solution) or Indole acetic acid, or Naphthol acetic acid to stimulate the ovary to form the fruit.

N.B. 1: Pollination provides the flower with male cells needed for fertilization of the ovules that develop into seeds, it also stimulates the auxins necessary for developing the ovary into a mature fruit even if fertilization does not take place.

N.B. 2: The maturation of the fruit and seeds often leads to discontinuity of the plant growth, and sometimes to its death, especially in annual plants. Due to consumption of stored food, and inhibition of hormones.

N.B. 3: If pollination and fertilization do not take place, the flower withers and drops off without fruit formation.

Reproduction in Human Being

Man belongs to class Mammalia in which the embryo develops inside the uterus till birth. Their eggs are small and nearly devoid of yolk. The number of young is few, due to parental care. Man shows a high degree of care, where the young requires several years of raising. This is due to mental progress that God provided him to be superior over other creatures.

The male genital system:

It consists of two testes; each testis leads to the tubules of the epididymis, the vas deferens, accessory glands till urethra. This system produces sperms and secretes male hormones whose function is to develop the secondary sex characters, i.e. the voice becomes deep, muscles grow stronger, and growth of facial hair….. etc.

A. The two testes:

The testis lies outside the body in the scrotal sac. During the last months of pregnancy for a male embryo; they move out of the main body cavity into the scrotum. Such a position prepares a condition cooler than the body temperature. This is suitable for spermatogenesis. If the testes fail to descend down into the scrotum, spermatogenesis does not occur, causing infertility.

The importance of the testes:

1. Production of sperms.

2. Secretion of Testosterone hormone, which causes the secondary male characteristics to appear at puberty.

B. The two epididymis:

Each testis leads to a group of cumulated tubes called epididymis, the latter fuses in the vas deferens.

C. The two vas deferens:

Each vas deferens transports sperms from the epididymis to a seminal vesicle.

D. The two seminal vesicles:

In which the sperms are stored until they leave the body.

E. Prostate gland and Cowper’s glands:

They secrete a sugary fluid (which nourishes sperms) and alkaline fluid to neutralize the acidity of the urethera. Since the neutral medium suits the passage of the sperms in it, therefore the alkaline fluid passes in the urethera just before the sperms.

F. The penis:

Is an organ that consists of a fibrous tissue. The urethera passes through it, through which both urine and sperms are expelled individually.

Study of a T.S. of testis:

The testis is built up of:

1. Seminiferous tubules among them these are interstitial cells which secrete the testosterone hormone.

2. Inside each tubule these are sertoli cells which secrete fluid to nourish the sperms inside the testis, they also have immunization function.

3. Each tubule is lined internally with diploid primary germ cells (2N), they are dividing, giving sperms finally.

Phases of spermatogenesis:

There are four main phases:

1. Multiplication phase:

In which the (2N) primary germ cells divide mitotically several times

giving great number of (2N) spermatogonia cells.

2. Growth phase:

In which the spermatogonia cells store an amount of food and are transformed into (2N) primary spermatocytes.

3. Maturation phase:

In which the (2N) primary spermatocytes undergo meiosis(I) to form (N) secondary spermatocytes which undergo meiosis(II) giving (N) haploid spermatids. (The number of chromosomes is reduced to its half during the maturation phase).

4. Metamorphosis phase:

In which the (N) spermatids are converted into (N) sperms.