How do I effectively visualize data showing change in a lot of samples over two time periods?
Two styles of graph come to mind.


A simple 2 layer histogram showing the distribution of gland counts for each year. This is a kernel density as opposed to a histogram, but it gets the idea across.

Line graph with year on the x-axis and gland count on the y-axis, with a colored line for each plant. This would show a little more detail, and would be better if the mean gland count overall did not change much, but decreased significantly among individuals.