The Science of Botanical Art

The Marvelous Mallows 

By Dick Rauh

Originally appeared in The Botanical Artist, Volume 14, Issue 3

 

The decision to place a group of plants into a family is based on similarity of features. Sometimes these features are so strikingly apparent to the viewer that the choice is obvious, other times the similarities may be largely hidden – molecular sequences perhaps or a particular nodal construction, or chemical peculiarities that defy outward appearance. Certainly we have become used to families that embrace a variety of habits. Look at the rose family for example, low-growing vining plants, herbs, prickly shrubs, and trees.  

Fortunately for us as flower painters it is the blossoms that are heavily leaned on to provide consistency. Stemming from Linnaeus, whose ‘artificial’ categories were based on the sexual variations in the forms of stamens and pistils, a good number of his observations still hold true, The reproductive apparatus of the pea family is so distinctive that it remains one of the most important features that hold that family together. Take a look next time you have the chance; ten stamens surround a single bean shaped pistil, the filaments of nine of the stamens fused into a tube, with a single uppermost stamen riding free on top. This doesn’t vary if you are looking at a clover, a garden pea, or a wisteria blossom. 

It is the flowers that provide the unity of the mallows. Whether we are painting an exuberant hibiscus, or its more circumspect cousin abutilon, there are certain features we can count on. First of all check the arrangement of petals. This is called imbricate, and each of the five petals is in front of the petal ahead of it and behind the petal coming up. This arrangement allows for a spiral unfolding of the petals, and for those genera that open and close, an opposite movement when closing. 

The petals in this family are distinct, which means separate, and unfused. In a number of genera the base of the petal narrows down, and there is a gap where the sepal lobes are visible. In a number of genera the corolla never fully opens up, and the reproductive organs, except for a protruding style are not visible.   But if we are ruthless in our quest for knowledge, and tear apart the petals, inside we will see the second strong character that defines this family. A rounded superior ovary of anywhere from 2 to many carpels (mostly 5 or 10 in the genera we paint) subtends a long style that at the apex divides into arms equal to the number of carpels, each crowned with a rounded stigma. 

But the androecium is the most distinctive organ. The filaments are fused into a sleeve that is adnate to the base of the corolla, and encloses the ovary, and the style, but never fuses to them. Towards the top of this sleeve numerous anthers appear, single instead of the usual pair, kidney-shaped and riding on their own filament that separates from the column. It is this spike of reproductive organs that thrusts up from the corolla that is unlike any other floral group. Its haze of anther sacs crowd towards the top with the apex of style arms and stigmas sometimes hidden in this mass of stamens. In hibiscus the filament sleeve often ends in a fringe that, although mostly hidden from view by the many anthers, is a delight to find and perhaps, if you can figure a way to show without losing track of the whole, a delight to paint. 

The calyx of five sepals is often fused into a cup, and in some species there are additional bracts that make up what is called the epicalyx. Smart plant. Some clever bees have found a way to get to the nectar by drilling through the calyx, thus voiding the whole point of the reward for pollination. To thwart this insidious theft, the plant provides protection in the form of additional bracts.

The fruit of the mallow is a schizocarp – a type of dry fruit that doesn’t split open to release its seeds, but instead splits as a carpel, remaining indehiscent to the end. The calyx is persistent on many genera, enclosing the schizocarp. In the case of the mallows the fruit resembles a tiny rounded Edam cheese! When the individual carpels called mesocarps split off, they look like nothing so much as a pie-shaped segment of cheese. The seeds remain inside this shell, until some outside vector disperses them, the same way all indehiscent fruit need outside forces to release their seeds. There is even one native mallow that is called ‘cheeses’ because of this special fruit type. 

Hollyhocks, rose of Sharon, rose mallow, as well as hibiscus and abutilon are members of this family, and the breeders have come up with some species where the flower begins to resemble a dinner plate – if size is one of the things that attracts you! As you paint the particular species that inspires you, don’t forget to emphasize those special characters that make this a member of  the Malvaceae.

 

  • Hibiscus rosa-sinensis, watercolor on paper, ©Barbara Klaas 2007