Campanulaceae
Introduction
This is a cosmopolitan family with showy flowers, mainly from the northern hemisphere, but in the southern hemisphere South Africa is particularly rich in members of this family.
Description
Description
In South Africa the family contains mostly herbs (annual, or perennial) or rarely small shrubs. The leaves are alternate, rarely opposite, simple, and without stipules.
The flowers are regular, bell-shaped, funnel-form or salver-form (corolla with a narrow tube and small spreading lobes) and bisexual. They are borne singly or more often in inflorescences. The large, showy flowers are predominantly blue in colour. Petals, sepals and stamens are normally in fives. The petals are partially or completely fused and are inserted on an inferior or half inferior or seldomly a superior ovary. There are as many stamens as corolla lobes. The style is simple with as many stigmas as carpels.
The fruit is a capsule.
Distribution and habitat
Distribution description
The Campanulaceae has a cosmopolitan distribution, although more abundant in temperate and subtropical regions, and consists of about 55 genera and more than 900 species. In South Africa there are 10 genera of which eight are endemic, and about 250 species. Some of the genera are discussed below.
The largest and most widespread genus is Wahlenbergia, which comprises 170 species. W. capensis is a common blue-flowered spring annual that is often found along roadsides and on open fields around Cape Town. Most of the annual species occur on the West Coast, as well as in the Northern Cape in sandy soil in open vegetation. Recently all 46 species of the shrubby genus Lightfootia have been placed in Wahlenbergia.
Roella is a genus of small shrubs found mainly in the southwestern Cape. Only one of the twenty-four species extends into the Eastern Cape and KwaZulu-Natal. Plants grow mainly on stony mountain slopes. Its large blue flowers are borne on the tips of branches in groups or singly. The best known species in this genus is R. ciliata.
Rhigiophyllum is one of two genera consisting of only a single species. The other one is Treichelia. Rhigiophyllum squarrosum is a small shrub, which occurs only in the Napier-Bredasdorp area, whereas Treichelia longebracteata is an annual known from a few localities in the Cape Peninsula and one in Hermanus.
Derivation of name and historical aspects
History
The regular and irregular flower shapes of members of the Campanulaceae have always been the subject of dispute and uncertainty. Some taxonomists prefer to consider the Campanulaceae as one complex, variable family with several subfamilies. New evidence from morphology and DNA sequence data has contributed to the current recognition of five subfamilies within the Campanulaceae: Campanuloideae, Lobelioideae, Cyphiodeae, Cyphocarpoideae and Nemacladiodeae. Only the Campanuloideae, Lobelioideae and Cyphiodeae are represented in South Africa, the other two subfamilies occurring in Chile, southwestern United States and northwestern Mexico. For the purpose of this article, I consider the Campanulaceae in the strict sense, that is, not recognising subfamilies, instead recognising the families Campanulaceae, Lobeliaceae and Cyphiaceae.
Class: Angiospermae (dicotyledons)
Order: Asterales
Ecology
Ecology
Many of shrubby members of the family which occur in the fire-prone fynbos vegetation of the southwestern Cape resprout after fire. Plants in the genus Merciera grow and flower most profusely in recently burnt veld. After six years, the plants start to die, disappearing when the veld remains unburnt for very long periods. Plants in the dry parts of the country have adapted to long periods of drought by developing an annual life cycle.
An interesting mechanism has been developed in the family to facilitate cross-pollination and hinder self-pollination. The flowers are distinctly protandrous (male reproductive organs mature first), and pollen is shed upon the style (with the stigma lobes closed up against one another) in the bud. The style is either sticky or hairy, to hold the pollen. This is the male stage in the development of the flower, and stamens wilt quickly as the corolla opens. After a time, when the bulk of the pollen has been carried away by insects, the stigma lobes unfold and the female stage sets in. The stigma is now ready to receive pollen from another plant.
Uses
Use
Species of the genera such as Wahlenbergia, Campanula, Symphyandra, Jasione and Phyteuma are popular garden ornamentals. Only Wahlenbergia occurs in South Africa. Occasionally Roella ciliata is planted as a garden ornamental.
I know of no cultural usage of members of the family.
In the garden Wahlenbergia undulata and W. rivularis are popular garden plants.
References
- Cupido, C.N. & Conrad, F. 1999. Bellflowers. Veld & Flora 85: 180-181
- Kovanda, M. 1978. Campanulaceae. In V.H. Heywood, Flowering plants of the world: 254-256. Oxford University Press, Oxford.
- Leistner, O.A. (ed). 2000. Seed plants of southern Africa: families and genera. Strelitzia 10. National Botanical Institute, Pretoria.
- Van der Walt, L. 2001-01. Wahlenbergia undulata (L.f.) A.DC. (Capanulaceae) on www. plantzafrica.com
Credits
Chris Cupido
Compton Herbarium, Kirstenbosch
September 2004
Plant Attributes:
Plant Type: Bi/Annual, Perennial, Shrub
SA Distribution:
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