Noses and Navels, Part 2: Navels

When I was a kid, boys ran around without shirts, all summer. We knew that there are kinds of navels - innies and outies. And so it is with roses and their relatives - the plums, peaches, cherries, apples, pears, loquats, etc. In this group, there are fruit types that are innies, and fruit types that are outies. For simplicity, I just refer to the whole bunch of these plants as roses.

Rose flowers, like all flowers, comprise a predictable array of flower parts (sepals, petals, stamens, and/or pistils) at the end of a special stem, a stem we call a peduncle. In the rose family, this arrangement usually has five sepals - which are often green and leafy, and fold back once the flower opens. The standard number of petals for roses is five also, and they are quintessentially normal - often white, pink, or red - though there are a lot of naturally-occuring roses with petals in the yellow and oranges, even in other colors. They are attached to this stem, this peduncle.

For many plants, the peduncle remains a simple stem tip, but in roses the peduncle (the flower stem) does neat things. It often forms a small shallow bowl, called a floral cup, in which case the sepals and petals are attached around the rim, with the sepals outside the petals. The peduncle can form more of a turban also, with parts mounded up, rather than sunken. As you might guess, flowers that form floral cups are going to become innies, and those with the mounds will develop into outies.

Most rose flowers are complete, having all of the four kinds of flower parts. Though the base situation is five sepals and five petals, stamens are often numerous, and pistils (ovaries) range from one to many. The stamens and pistils can all be crammed down in the floral cup, or will be raised on a mound, depending on the genus.

When the flower develops into a fruit, the stem often becomes exaggerated. For garden variety rose, plants in the genus Rosa, the flower forms a floral cup, which wraps loosely around the pistils and stamens. With fruiting the cup turns into the rose hip, with its crown of triangular, leafy sepals and its mop of dead stamens and developing pistils poking out the end. In the world of navels, this is an innie.

What if the floral cup were more absolute in its ability to grow around the pistils, if even in flower the cup more tightly surrounded the pistils? Then when the fruit develops, the stem becomes really fleshy and takes on an absolute shape. You could then have an apple or a pear - that is how they develop. So the flesh of an apple, and that of a pear, are basically stem tissue, and in their true complexity bear layers of tissue that come from the bases of sepals and petals also. These would be super-innies.

If the stem forms exactly in the opposite way, making a dome rather than a cup, you find the pistils sitting on top of a bulging stem tip, rather than sunken. This is a pretty normal arrangement in many other flower groups, the magnolias and the anemones, for example. In the roses, you find such an arrangement in many genera, but it is mostly grandly expressed in the strawberry. Check out a strawberry flower (genus Fragaria) with a handlens, and you will see tiny little pistils making a beaded spiral in a central mound. Even though there are numerous separate pistils, this is still a single flower. As the fruit develop (each of the little pistils becomes a separate fruit), the stem also inflates to a beautiful, red, fleshy strawberry - with its little hard, mature one-seeded fruit arranged like tiny jewels. This is a real outie.

But it doesn't end there. In some roses, each pistil develops a fleshy covering (its own fleshy fruit), every one standing out as a separate fleshy bead. In Rubus, the blackberries (and raspberries,and dewberries, and ollalieberries,) there are several pistils on the flower stem. When blackberries mature, the stem is normal, but each pistil is fleshy. So a blackberry is an outie also - a set of lovely fleshy fruit formed on the stem of a single flower.

And what if it is all just much simpler? If there is no floral cup, and if the stem is kinda normal, and if there is only one pistil, which turns into a fruit without any added stem. And because roses only produce one seed in each pistil, the fruit is one-seeded. Then you have the genus Prunus, which includes the peaches, plums, apricots, cherries, and almonds. Each of these is less-messy affair, developing from a flower that had only one pistil, with its sepals at the base rather than at the tip.

So the roses are really funny. With incredibly minor changes in what is fleshy and what is not, in what enlarges and what stays small, the same basic floral arrangement yields fruit so very different as rose hips, apples, strawberries, blackberries, and peaches. Some are innies, some are outies, and some don't even have navels. Perhaps, then, it is too simplistic to think that a rose, is a rose, is a rose.