Hayes and Garber - Cucurbit Breeding

PLANT GENETICS 17
developed to explain Mendelian heredity, it will be necessary to
give some of the main facts of reproduction in plants.
The Mode of Sexual Reproduction in Flowering Plants.
Nearly all higher plants produce seeds as the result of the union
of sexual cells or gametes. Each body cell which is capable of
further division contains a nucleus in which the" chromatin is
located. This chromatin, which is composed of a definite number
of parts or chromosomes, gains its name from the fact that it
takes a dark stain with certain reagents when other parts of the
Femaip,
LA
Archesporial or megaspore
mother cell
Male
Archesporial, cell
Reduction division
Period
Nucleus with of
chromosomes divisio
Embryo sac
^Syaergids
Egg cell or female garnet
-Embryo sac
,,
Polar or endosperm nuclei
Antipodal cells of
nutritional value
4 -celled stage
or tetrad
Pollen
\grain
53-Tube
/ nucleus
Generative
nucleus
FIG. 3. Diagram to illustrate production of male and female gametes. A,
In some forms as Lilium this megaspore mother cell functions directly as the
embryo sac. Reduction division in Lilium occurs at the first nuclear division
within the embryo sac.
cell are unstained.
In the soma or body of the plant the nucleus
of each cell contains a definite number of chromosomes, half of
which were obtained from the male sexual cell and half from the
egg cell. Each new body cell results from the longitudinal
division of the chromosomes of a preceding body cell. Thus
all of the somatic cells of a plant contain the same number of
chromosomes.
Preparatory to the formation of the germ cells or gametes,
the chromosomes assume a paired condition, one member of each
2