In this course, three taxonomic categories feature prominently: family, genus, and species. Of these three, the family is the most inclusive group. Families frequently may correspond to well-known groups, such as grasses (Poaceae), orchids (Orchidaceae), mustards (Brassicaceae), or beans (Fabaceae). Families are grouped into orders in the taxonomic hierarchy.
Note the way in which the scientific name of a family is formed: by the name of an included genus, or kind of plant, plus the ending -aceae. However, some families may also have older names that do not conform to this pattern (for instance, "Compositae" is an older name for the daisy family, Asteraceae). Where these occur they will be indicated parenthetically. Note too that the family names above were explained by reference to English common names (grasses, orchids, mustards, beans) as these were thought to be familiar to most readers of this web page.
Members of a family (i.e. genera) typically share many morphological, chemical, or anatomical features that set them apart from other families. Many of the morphological features that, at least in part, define families are characteristics of their flowers or fruits, such as the arrangement of parts in a mustard flower (Brassicaceae), the pod of the bean family (Fabaceae), or the way in which the fruits of the parsley family (Apiaceae) come apart. These shared, derived features ("synapomorphies") are often seen as evidence that members of a family share a single common ancestor, and so are monophyletic (see pp. 13-18 in Zomlefer, 1994).
The complete names of plant taxa include identification of the authority responsible for the name, or for the combination in which it appears. Click here to learn more about authorities. Each name of a family is also associated with a type genus; consult a textbook on plant taxonomy in order to learn more about the type method as practiced by botanical systematists. The standard form for the names of plant taxa can be accessed on the International Plant Names Index (IPNI) web site.
Click here for information on modern usage of family names, or view the same essay in .
| What are plant families? | How do we distinguish them? | How and why do we study them? | Selected vascular plant families of Ontario | Reading List | Course outline |
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