Excerpts from Jim Conrad's
from the April 15, 2012 Newsletter issued from the woods of the Loess Hill Region a few miles east of Natchez, Mississippi, USA
The leaves of pear and apple trees are fairly different and certainly the fruits are easy to distinguish, but the flowers are surprisingly similar. For example, compare the pear flowers at the top of the page at http://www.backyardnature.net/n/w/pear.htm with the apple flowers shown above.
The similarities aren't surprising, since both apple and pear species are members of the Rose Family, and cladistic analysis shows that they are very close to one another, if not inclusive, on the phylogenetic Tree of Life.
If you ever need to distinguish an apple flower from a pear flower there's a little secret to help you. It's that the pear blossom's several styles -- the slender ovary "necks" connecting the ovary with its pollen-receiving stigmas -- are usually separate from another all the way to their bases, while in apple blossoms the styles usually join with one another above their bases.
You might like to compare our longitudinal section of a pear flower at http://www.backyardnature.net/n/09/090309ps.jpg with the apple flower section shown below. Notice that in the pear flower's center the greenish styles remain separated all the way down to where they enter the green tissue that later will become the pear, but those of the apple flower below fuse above the ovary: