These consist of a series of columns representing a variation in frequency (the number of times an event occurs) of a variable over a discrete interval or class. The example given shows the frequency of flowers in the flower heads of a sample taken from a population of red clover. It is worth noting that the area beneath the histogram is proportional to the frequency of the items being recorded. This is more easily demonstrated on graph paper where you can count up the squares under the columns of the histogram.

The distribution of the number of flowers per flower head in a population of red clover Trifolium repens

These are very like histograms except that the columns are not usually adjacent to one another. This is to emphasise the point that these data are not directly related to one another. They could be placed in any order.

The effect of different mineral solutions on the
germination of lettuce seeds after two days