Gametes produced by the parents are shown along the and sides of the Punnett square.

Vertical and horizontal

Explanation:

A punnet square is a tabular chart used in genetics to display the genotypic composition of the offsprings of two parents. To construct a punnet square, the alleles of the gametes produced by the parents is required.

The gametes produced by each parent via meiosis are placed along the vertical and horizontal sides of the punnet square. For example, if a cross occurs between two parents with the following genotype: AaBb and AAbb. The parents will produce the following gametes:

AaBb - AB, Ab, aB, ab

AAbb - Ab, Ab, Ab, Ab

These gametes produces by each parent will be placed along the sides (vertical and horizontal) of a punnet square to determine the genotype of the offsprings that will be produced.

Typically, it takes between 500 to 1000 years for a primary succession to reach a climax community. 
A primary succession usually begin in bare place with may be only rocks or soil while a climax community is a mature community that signifies the end of growth of a community. It takes year for a primary succession to become a climax community.