Heterozygous Tall Plants:
When two heterozygous tall plants are intercrossed, it means that both plants have one dominant allele for tallness (T) and one recessive allele for shortness (t). These plants are referred to as Tt.

Mendelian Inheritance:
To understand the inheritance pattern of the trait, we need to consider Mendelian genetics. According to Mendel's laws of inheritance, each parent contributes one allele to their offspring. Therefore, in this case, each parent can contribute either the dominant allele (T) or the recessive allele (t) to their offspring.

Punnett Square:
To determine the percentage of progeny that will be homozygous tall, we can use a Punnett square. A Punnett square is a grid used to predict the possible genotypes of offspring from a cross between two parents.

Genotypes of the Parents:
Let's assume that the two heterozygous tall plants are represented as Tt1 and Tt2.

Possible Gametes:
Each parent can produce two types of gametes, one with the dominant allele (T) and one with the recessive allele (t). Therefore, the possible gametes for Tt1 are T and t, and for Tt2 are also T and t.

Punnett Square:
To construct a Punnett square, we need to place the possible gametes from one parent along the top of the square and the possible gametes from the other parent along the side of the square. Then, we fill in the boxes with the combination of the gametes.

The Punnett square for the given cross would look like this:
```
T t
T TT Tt
t Tt tt
```

Phenotypes and Genotypes of Progeny:
From the Punnett square, we can determine the genotypes and phenotypes of the progeny. The genotypes are represented by the letters (T or t) in each box, and the phenotypes are determined by the expression of the dominant allele (T) for tallness.

In the Punnett square, there are 4 boxes. Out of these 4 boxes, 3 have the genotype Tt and 1 has the genotype TT. Therefore, 3/4 or 75% of the progeny will have the genotype Tt (heterozygous tall), and 1/4 or 25% of the progeny will have the genotype TT (homozygous tall).

Conclusion:
In summary, when two heterozygous tall plants are intercrossed, 25% of the progeny will be homozygous tall (TT) and 75% of the progeny will be heterozygous tall (Tt). This follows the principles of Mendelian inheritance and can be determined using a Punnett square.