Scientific names, those italicized (or underlined) two-word names we often see in plant catalogs, consist of the genus (always capitalized and italicized) and the species (always lower case and italicized), plus the name of the person who originally provided the name (called the ‘authority’; often shortened and never italicized). In conversation, you needn’t include the authority (so don’t bother to learn that part), but, when written, the authority’s name is included the first time the species is mentioned. Two authorities encountered frequently here and elsewhere are L., for Carl Linnaeus, the 18th-century taxonomist who invented the nomenclature system still in use today, and A. Nelson, one of “ours.” Aven Nelson arrived in Wyoming in 1889 to take a position at the new University of Wyoming and spent most of his life here. He and his wife Ruth Ashton Nelson botanized widely in the state, region, and beyond, discovering and describing many now-well-known western plants.
Scientific names used in this publication are based on Vascular Plants of Wyoming, 3rd ed. (Dorn, 2001). In a few cases, these names conflict with USDA PLANTS Database (plants.usda.gov), in which case we have provided the USDA name as a synonym. The PLANTS Database was also used to confirm common names.
In a typical flower, the outermost whorl of sepals surrounds and protects the bud; they are usually green and can be found beneath the open flower. The showy petals are next. The male structures are called stamens; each consists of a filament (stalk) topped by an anther, where pollen is produced. The female structure is the pistil, made up of (from the top down) the stigma (sticky part that receives pollen), the style (stalk), and the ovary, in which the eggs are hidden.
Of course, there are all kinds of variations on this basic arrangement of parts. For example, some flowers lack petals. Pasqueflowers have showy sepals to attract insects, while wind-pollinated plants, like grasses, having dispensed with showiness altogether, lack both sepals and petals. Columbines, lilies, and sulfur flowers, among others, have equally showy sepals and petals. Together, sepals and petals are called the corolla, and if they cannot be distinguished, then they are called tepals.
Members of the Mallow family (Malvaceae) (such as hollyhocks) have many stamens, and the filaments are fused into a tube that surrounds the style. Such an arrangement is called monadelphous, and is characteristic for mallows, but encountered elsewhere, too. In the Penstemons, there is a sterile, hairy structure, presumed to have evolved from a stamen, called the staminode. The staminode probably serves to force insect visitors in the correct direction to pollinate the flower and may prevent inefficient pollinators from entering the flowers.
Members of the sunflower family (Asteraceae) are more interesting yet! What we perceive as a single flower is really a bunch of very small flowers, called florets. Disc florets, in the center of “ordinary” sunflowers, have five little petals fused into a tube, five stamens with anthers fused into a tube, and a pistil that extends through the anther tube and unfurls its two curled branches. Ray florets form the outer ring of sunflowers; their five petals are fused into a single, large ray, and they are often sterile. Although thistles (and thistle-like flowers) and dandelions (and similar flowers) have slightly different kinds of florets, all of these plants have compound flowers, with each floret making a single one-seeded fruit. This is obviously a very successful strategy—Asteraceae is the most diverse family in the world, with an impressive 111 genera represented in Wyoming!
An inflorescence is just a botanist’s term for a cluster of flowers. Sometimes an inflorescence might look like a single flower, as is the case with daisies.
The simplest leaf shapes are called simple, meaning that they are all in one piece, and lack large protrusions and indentations (such as a lilac leaf). Other options for leaves are lobed and compound. Lobed leaves have large protrusions, and compound leaves are dived into more than one leaflet. Oak and maple leaves are good examples of lobed leaves, and also illustrate the difference between palmate and pinnate: Oaks are pinnately lobed (lobes opposite each other across the midvein), and maples are palmately lobed (all lobes with a common origin, like fingers from the palm of your hand). Compound leaves are also pinnate (such as on caragana shrubs) or palmate (such as on lupines) in the same way.