Basal Angiosperms

The Basal Angiosperms are comprised of a few separate evolutionary groups that branched off from other flowering plants at successive occasions before the appearance of the "true" dicots (Eudicots). Although Dicots and Monocots may generally be told apart by a combination of characteristics (two seedling leaves vs. one, net vs. parallel leaf veination, circularly arranged vs. scattered vascular bundles, flower parts in multiples of 4 or 5 vs. multiples of 3, etc.), the basal angiosperms do not fit well into either category, although they were once grouped with dicots due to their leaf veination and two seedling leaves (cotyledons). Basal Angiosperms often show combinations of the following traits: numerous flattened (laminar) stamens with wide filaments; numerous tepals; many separate carpels; aromatic oils (giving them a "primative" odor); and alternate, spirally arranged leaves. Most also share the microscopic characteristic of monosulcate, or monoaperturate pollen (also seen in monocots). Phylotaxis, which isn't always readily observable except during early development, was probably spiral in the flowers of the ancestor of all angiosperms. A transition to developing floral organs in whorls of 3 most likely occurred early on, however. There has been debate as to whether a secondarily dioecious shrub from New Caledonia, Amborella, is the sole representative of the basalmost-branching lineage of angiosperms or whether that lineage also should include the angiosperm order containing Water Lilies, Nymphaeales. Nymphaeles and Amborella both seem to lack vessel elements homologous to those seen in practically all other angiosperms, supporting the view that the earliest angiosperms, like gymnosperms, lacked vessels. They also both lack the ethereal oils (and thus the "primative odor" that are present in most other basal angiosperm lineages. Although most basal angiosperm families aren't represented in central PA, they contain most of the variation in floral structure and arrangement within flowering plants.

Purple denotes orders containing families covered in class; green denotes orders photographically represented but not covered in Biology 414.

Click on the tree to skip directly to a given order.

Basal angiosperm families covered in class:

Nymphaeales:

Nymphaeaceae (Water-Lily Family)

Magnoliales:

Magnoliaceae (Magnolia Family)

Piperales:

Aristolochiaceae (Birthwort Family)

Laurales:

Lauraceae (Laurel Family)

Order: Nymphaeales

*Nymphaeaceae: (Water-Lily Family)

Identification characteristics: The flowers of Water Lilies are variable in morphology, but are usually readily identifiable. They usually have few sepals (3-6) which merge into petaloid structures. There is some recent research suggesting that the perianth parts should all be considered tepals despite the fact that they are visually distinct. The petals may be small and reduced or may be staminoid in structure. Often, the petals become more and more stamen-like until they eventually intergrade with the fertile, laminar stamens. The ovary is usually at least partially inferior and most often produces a leathery berry that ruptures irregularly, releasing seeds which are generally water-dispersed. Occasionally, separate carpels and superior ovaries may occur, particularly if the described family Cabombaceae is included within Nymphaeaceae. The leaves are usually cordate to sagittate at the base, and petioles, peduncles, and flower buds are covered in slimy mucilage. With their showy flowers and aquatic habit, the only plant family likely to be confused with Nymphaeaceae is the unrelated Nelumbonaceae, which has peltate leaves and a superior ovary that forms a unique fruit-type (not at all like a leathery berry).

Interesting stuff: There is some debate over what lineage of plants is basalmost amongst angiosperms (i.e. the sister group to all other angiosperms). There is little doubt that water-lilies are either part of this first branching lineage or are the second-branching lineage. In either case, despite their aquatic habitat (likely a derived character state), study of water-lily floral and vegetative structure is certain to provide insight into what features were present in the ancestor of all modern day angiosperms. Water-lilies were once hypothesized to be relatives of monocots because of similarities in pollen morphology and vascular arrangement. Water-lilies are an important ornamental component of water gardens around the world. Cabombaceae is listed as a separate family in your manual.

Nuphar advena Spatterdock, Yellow Pond Lily, Cow Lily- Despite being aquatic, the emergent flowers of Spatterdock and other water lilies attract numerous insects.

Nymphaea odorata var. tuberosa Tuberous Water-Lily- This variety has unscented flowers. Water-Lilies are among the basalmost angiosperms.

Order: Illiciales

Illiciaceae:

Illicium floridanum American Star Anise (Native to S.E. United States)- All parts of this pretty-flowered shrub release a pleasant fragrance when crushed.

Order: Magnoliales:

Annonaceae:

Asimina triloba Pawpaw- Pawpaw flowers smell terrible and are often found with maggots inside. They must outcross to produce their variably tasty fruit.

*Magnoliaceae: (Magnolia Family)

Identification characteristics: Magnoliaceae have tepals in multiples of three which range in number from 6 to many. The outer 3 are often distinctly more sepaloid. The stamens are numerous and laminar. Carpels are numerous and arranged on an elongate receptacle in cone-like fashion. These separate carpels may sometimes form follicles that partialy fuse before releasing arillate seeds, or may stay separate as an aggregation of wind-borne samaras. Leaves of Magnoliaceae are alternate and show a characteristic ring around the stem (a scar left by the deciduous stipules) at every petiole base and old node. Magnoliaceae also produce volatile oils that often make their vegetation aromatic when crushed.

Interesting stuff: Magnoliaceae were once hypothesized to be the basalmost angiosperm family due to the resemblance of their gynoecium to the cones of gymnosperms. However, phylogeny and development show clearly that this resemblance is superficial, and the structures are non-homologous. Magnolias and Tulip Tree are well-known ornamentals and valued timber trees.

Liriodendron tulipifera Tulip Tree- Also known as Tulip Poplar or Yellow Poplar, this large, straight-trunked forest tree is prized by the timber industry.

Liriodendron tulipifera Tulip Tree- Some people ascertain that this tree is named after its tulip-like flowers; others claim that the leaves are tulip-shaped.

Liriodendron tulipifera Tulip Tree (fruit)- Unlike other Magnoliaceae, Tulip Tree forms a cone of dry, wind dispersed achenes formed from numerous separate carpels.

Order: Piperales

*Aristolochiaceae: (Birthwort Family)

Identification chracteristics: Flowers in Aristolochiaceae may be zygomorphic or actinomorphic. Most members lack petals, but have three pigmented sepals that are fused together. There are 6 to 12 stamens that are often fused to the style, and the inferior ovary is comprised of 4 to 6 fused carpels. Most species produce capsules as the fruit. Aristolochiaceae have alternate leaves that are very often reniform in outline.

Interesting stuff: Many members of Aristolochiaceae produce maroon or brownish, foetid flowers that are carrion fly or beetle pollinated. The genus Aristolochia produces elaborate, curved calyx tubes that often trap flies until the flower withers. Members of the genus are often called "Pipevine" or "Dutchman's Pipe" for their shape. Some Aristolochia are planted as ornamental vines, and some members of the genus Asarum are used as groundcovers for their fast-spreading, rhizomatous habit.

Asarum canadense Wild Ginger- True ginger is a monocot, but the roots of the paleoherb Asarum have a very similar scent when crushed.

Asarum canadense Wild Ginger- The somewhat transluscent areas inside Asarum flowers expedite pollination by guiding pollinators into the flower.

Asarum canadense Wild Ginger- The furryness and color of A. canadense flowers, along with their foetid scent tricks carrion beetles and flies into visiting.

Saururaceae:

Saururus cernuus Lizard's Tail- Lizard's Tail is typically found in swampy sites. The individual flowers are small, but the collection of many makes the"tail" attractive.

Order: Laurales

*Lauraceae: (Laurel Family)

Identification characteristics: Lauraceae are alternately-leaved shrubs or trees in our range. They can be identified by their 6 tepals, usually 9 stamens, anthers which release pollen through flapped valves, and a unilocular, superior ovary which forms a drupe as the fruit. Many species are dioecious, and many possess staminodes or glands in place of one or more whorls of stamens. All vegetative parts of Lauraceae are extremely fragrant when broken due to copius quantities of volatile turpenoids.

Interesting stuff: Lauraceae are one of the largest basal angiosperm families and are common in tropical forests. One genus, Cassytha, is parasitic and viney, strongly resembling members of the genus Cuscuta (Convolvulaceae: in Asterids) in a striking case of convergent evolution. Bay leaves, cinnamon, and avocado are important economically. Sassafras root was once the 2nd largest export from North America (behind tobacco) in colonial times, but tea and root beer produced from it has fallen into disfavor because of the presence of small quantities of carcinogenic compounds therein.

Lindera benzoin Spicebush (male inflorescence)- These male flowers of Lindera show anthers opening via flaps, typical of Lauraceae.

Sassafras albidum Sassafras (male flowers)- The inner 3 stamens have paired glands at their base; the anther valves open slightly differently from the outer 6 stamens.

Sassafras albidum Sassafras (female flowers)- The female flowers of Sassafras have sterile staminodes. The ovary eventually becomes a bluish drupe.

Sassafras albidum Sassafras (female inflorescence)- Leaves of Sassafras, when they emerge, come in 3 different lobed forms as well as an unlobed form.

Sassafras albidum Sassafras (female flowers)- The unilocular ovary with one globose stigma topping the style is probably formed from one carpel.