Boraginaceae

▪ plant family

  borage or forget-me-not family of flowering plants, with 148 genera and more than 2,700 species. In the earlier Cronquist botanical classification system, it was placed in the order Lamiales, and, in the first version of the Angiosperm Phylogeny Group (APG) system, it was treated as part of Solanales. Although it clearly belongs in the vicinity of these orders in the Asterids I lineage, its position is still uncertain. For information on the revised Angiosperm Phylogeny Group II (APG II) botanical classification system, see angiosperm.

 Boraginaceae was initially put into Lamiales because it shared with Lamiaceae (mints (mint)) and Verbenaceae (vervains) ovaries with four deeply divided partitions, a style attached to the base of the ovary, and fruits that break apart into four nutlets. These similarities appear to have evolved independently, however, and borages differ in having alternate leaves, round stems, different secondary metabolites (no iridoid alkaloids), regular flowers, the same number of stamens and petals, and flower clusters that are often coiled like a scorpion's tail. The family includes a number of garden ornamentals, such as Heliotropium ( heliotrope), Mertensia virginica (Virginia bluebell), Pulmonaria ( lungwort), and Myosotis ( forget-me-not). Some of the more typical borages show colour changes of the corolla upon aging, from pink to blue, yellow to pink to blue, or yellow to white; this transformation is caused by changes in the pH of the cell sap. Many species are poisonous, and some species have been used medicinally, such as Borago officinalis ( borage), Symphytum officinalis ( comfrey), and Lithospermum ( puccoon). In the tropics the genus Cordia, with more than 200 species, is very diverse and includes some important timber species.

 Two other groups, which were formerly treated as separate families, have been reassigned to Boraginaceae based on molecular and other evidence. One group is Lennoaceae, or the sand food family, with three genera and seven species of root-parasites that have small, scalelike leaves and totally lack chlorophyll; they inhabit desert regions in Colombia, Venezuela, and the southwestern United States. They have typically boragelike flowers, but their ovaries are divided into many partitions. The other group is Hydrophyllaceae, or waterleafs (waterleaf). It includes ornamentals such as Phacelia (150 species), Hydrophyllum, and Wigandia. They differ from other borages in their parietal placentation and more numerous seeds.

Paul E. Berry

 

* * *