Mendel studied 7 contrasting character of garden pea, Pisum sdtivum, which were present on 4 chromosomes. A pea plant is having 14 chromosomes as diploid. number. If the chromosome would have been 12, it means that they should be present on 6 chromosome this suggest that the 2 or more characters are linked. So, later researches found it to be so due to linked character (linkage).