![The Papaveraceae [Illustration by Elizabeth Twining]](papaveraceae-large-ElizabethTwining.jpg)
Families with 4 petals and the Fabaceae
This lesson covers families of plants that have four petals. Most plant families have flowers with five or three petals. There are fewer families with four petals. The families you will learn to recognize in this class are:
The Papaveraceae (the poppy family)
The Brassicaceae (the mustard family)
The Onagraceae (the evening primrose family)
These can be distinguished from each other based on the position of the ovary and the number of stamens.
This lesson will also cover the main subfamily (the Papilionoideae) of the Fabaceae (the legumes, or pea/bean family). These plants have five petals, but two are fused together.
The Papaveraceae is the poppy family. Plants of the Papaveraceae have...
The sepals often fall off the flower early, so you may not see them in open flowers. (Look at the youngest flowers to see sepals.)
Many species have petals that are "creped" (with longitudinal, fine wrinkles), as in the poppy above.
Some members of the Papaveraceae, such as the prickly poppy (below) have 6 petals.
(On a side note: the image above, the leaves have clasping leaf bases. This is not a characteristic of the entire family.)
The Brassicaceae is the mustard family. This family used to be called the Cruciferae, due to the cross shape that is typically formed by its four petals
.Plants of the Brassicaceae have...
In the images above, you can see all six stamens (four long, two short) in a dissected mustard flower (in this case, a flower from which perianth parts have been removed; Gray 1887). The image on the right shows both a longitudinal section of the flower (with two of the 4 long stamens) and a floral diagram showing placement of the stamens (Groom 1898). In the floral diagram, the black curved arcs represent sepals, the white or open curved arcs represent petals, and the small two-lobed black dots represent stamens. The cross-section of the ovary, with the central partition is also shown. When this ovary becomes a fruit, the seeds will remain attached to this thin, central partition, and the side walls of the fruit (the valves) will split away from this seed-bearing partition. (See the dehisced silique in the first illustration on this page.)
Short siliques are called silicles.
The species below produces silicles. This illustration shows many intact fruits, an enlargement of a fruit that has lost one of the fruit valves, and an enlargement of a fruit that has fully dehisced and lost both fruit valves (lower right corner).
The Onagraceae is often called the evening-primrose family. It is the only one of these 4-petal families that has an inferior ovary.
Plants of the Onagraceae have...
In the black-and-white drawings of enlargements and dissections above, figure 4a came from the top (distal end) of figure 4b:
On the yellow-flowered species below, identify parts:
The Fabaceae is the pea or bean family. An older name for the family is Leguminosae, and members of this family are often refered to as legumes.
The flowers vary by subfamily. There are three subfamilies of the Fabaceae, but you will only be responsible for recognizing one: the Papilionoideae. The flowers of this subfamily are the typical "pea flower". These flowers...
The other subfamilies are present in California. They include the
Caesalpinoideae, whose flower resembles the pea flower above, but whose banner is inside the wings, rather than outside. Western redbud (Cercis occidentalis) is in this subfamily. Note the position of the banner and wings.
The third subfamily, the Mimosoideae, has radially symmetrical flowers. It's members are mostly in tropical and subtropical regions, but California does have some. Prosopis (mesquite) is a member of this subfamily.
The fruit of species in the Fabaceae is usually a legume. In some species it is a loment. (A loment is an elongate legume-like fruit that breaks into single-seeded sections.)
Leaves of plants in the Fabaceae are...
Leaves may be pinnately compound or palmately compound.
If leaves are pinnately compound, they may end in a leaflet, a pair of leaflets, or a tendril. Leaves having an odd number of leaflets are called "odd-pinnate". Leaves that have an even number of leaflets are callded "even-pinnate". You do not have to count leaflets to determine this; just look at the tip of the leaf. Does it end in a single, terminal leaflet? If so, it is odd pinnate. Does it end in a pair of leaflets? If so, it is even-pinnate.
Check your understanding:
Use the photo below to answer the questions that follow.
